Answer: 21.32 per hour
Explanation:
Guitars produced each month = 100
considered good enough to sell = 82%
Remaining are scrapped = 18 %
Selling price of each guitar = $260
Each guitar requires = 10 labor hours
Each employee works an average = 160 hours per month
Labor is paid = $11 per hour
materials cost = $40 per guitar
overhead = $4,200
Therefore,
Number of guitars are good enough to sell = 82% of 100
= 82 guitars
Value of output = Number of guitars sell × Selling price of each guitar
= 82 × $260
= $21,320
Input in labor hours = Guitars produced each month × Labor hour employed in each guitar
= 100 × 10
= 1,000 hours
Labor productivity =
= 
= 21.32 per hour