Question 461227
Scenario I:
C1 = 4*25 + 4*X*10 [$], where X: number of hours/day

Scenario II:
C2 = 4*X*15 [$], where X: number of hours/day

For X > 5 (more than 5 hours of work per day) Scenario I is the cheapest strategy.
For X = 5 , C1 = C2
For X < 5 , C2 < C1