The fee is $105 for 12.5 hours, then to find the unit rate we do the quotient:
105 / 12.5 = $8.4 per hour.
Now Part B:
Then, for 40 hours, we simply multiply $8.4 times 40 and get: $336.
So the cost will be $336 per 40 hours.
Please notice that I typed 8.4 (eight POINT four) not 8/4.
if they want it in fraction form you should type: 42/5
Did you complete part B as well?