Can the team clear the winter repair backlog without overtime?
Convert a repair mix to staff hours. Then compare two ways to cover a winter shortfall.
The question
Boreal Repairs is a fictional Canadian warranty depot. Complete all 800 jobs this month at the lowest extra cash cost. Salaried labor supplies 800 hours at a fixed cost. The vendor and overtime options meet the same service standard for this exercise.
| Value | |
|---|---|
| Repair jobs | 800 |
| Minor jobs | 70% |
| Major jobs | 30% |
| Hours per minor job | 0.5 |
| Hours per major job | 2 |
| Salaried staff hours | 800 |
| Vendor capacity, major jobs | 90 |
| Vendor, CAD per major job | 90 |
| Overtime, CAD per hour | 60 |
Each vendor job frees its full internal repair time. No coordination time is assumed.
A vendor can take up to 90 major jobs at CAD90 per job. Overtime costs CAD60 per hour. Each major job sent to the vendor frees two internal hours. There is no vendor coordination time in this exercise.
“Can the depot finish with salaried hours? A winter diagnostic changes the major-job share to 45%. Which additional capacity should the depot buy?”
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A strong answer, step by step
Open each step in turn. This is one strong answer, not the only one.
Step 1: Which evidence gives the staff requirement?
What would you do here? Open the move you’d make.
Start from vendor price per major job.
Tempting, but it misses something. That becomes useful after you establish whether extra capacity is needed.
Use the average of 0.5 and 2 hours.
Tempting, but it misses something. An unweighted average assumes equal numbers of both jobs.
Multiply each job type’s count by its time.
The strong move. It converts the actual mix into comparable staff hours.
See how a strong candidate says it
“I need the number of jobs, the minor/major mix and the time per job. An 800-job queue is not an 800-hour workload.”
Why it works: The mix weights each repair time by how often that job occurs.
Step 2: How many hours does the initial mix require?
What would you do here? Open the move you’d make.
Use the weighted total and compare it with 800 hours.
The strong move. The same unit on both sides shows whether the depot needs extra capacity.
Plan for 1,000 hours from 1.25 hours per job.
Tempting, but it misses something. The average gives minor and major jobs equal weight, contrary to the exhibit.
Compare only the 480 major-job hours with capacity.
Tempting, but it misses something. Minor repairs still require 280 hours.
See how a strong candidate says it
“There are 560 minor jobs × 0.5 hours = 280 hours and 240 major jobs × 2 hours = 480 hours. Total 760 hours, leaving 40 of the 800 salaried hours free.”
Why it works: The job counts and hours reconcile separately.
Step 3: Should the depot buy capacity now?
What would you do here? Open the move you’d make.
Reserve and pay for all 90 vendor slots now.
Tempting, but it misses something. That incurs cash cost for spare capacity under the supplied forecast.
Schedule the work in-house and check the repair mix again.
The strong move. This uses existing capacity and monitors the assumption most likely to change the result.
Move all major jobs to overtime.
Tempting, but it misses something. The existing staff can do the work without overtime, so this increases cash cost.
See how a strong candidate says it
“No. Keep the original 800-job workload in-house. It fits by 40 hours. Check the diagnostic mix before the schedule is locked.”
Why it works: The objective is lowest extra cash cost for on-time completion; no extra capacity is needed yet.
Step 4: Major jobs rise to 45%. Which capacity costs less?
What would you do here? Open the move you’d make.
Buy 140 overtime hours because CAD60 is below CAD90.
Tempting, but it misses something. That compares one hour with one major job. A major job frees two hours.
Outsource all 90 allowed jobs to maximize spare time.
Tempting, but it misses something. It meets the deadline but costs more than the 70 jobs needed.
Outsource 70 major jobs if the vendor meets the deadline.
The strong move. It covers the shortfall for CAD2,100 less than overtime.
See how a strong candidate says it
“The new mix needs 940 hours, so the shortfall is 140. Send 70 major jobs to the vendor for CAD6,300. Overtime for 140 hours would cost CAD8,400. Confirm the vendor can deliver the 70 jobs on time.”
Why it works: Compare cost for the same 140 freed hours. Existing salary is fixed in both options.
The answer, in short
- Decision
- Use the vendor for 70 major jobs under the changed mix.
- Because
- The vendor frees 140 hours for CAD6,300, compared with CAD8,400 in overtime.
- What would change it
- If the vendor can take only 50 jobs, use it for those jobs and buy the remaining 40 hours as overtime.
Common traps
- Using an unweighted mean.
- Comparing cost per job with cost per hour.
- Subtracting an imagined salary saving from vendor cost.
Check your answer
- Did you calculate 760 hours at the initial mix?
- Did you identify the 140-hour shortfall after the change?
- Did you round vendor jobs up to a whole job when needed?
- Did you compare extra cash costs for the same capacity?
Last reviewed Nov 11, 2026