Past paper 1 december 2014

Hi My Dear Tutor, question 3 relevant cost.

Relevant costing notes 3.

If i have 200 hours available and if 150 hours are idle will be paid anyway and the remaining hours are 50 and 40 hours per week.
Total hours—-200
idle————-150
the remaining-50

why did you calculate 40*1.5*16=1200

My question here is that since there are remaining 50 hours out of 200 total hours how we can calculate overtime?40 hours per week and plus 10 hrs equal to 50 hours which are part of total 200hours.I do not understand this part of question.how i can calculate overtime pay for 10 hrs since it is included into 200 hours?