Question 315894
a) Option 1: $25 per day for 4 days means you pay a fixed cost of $100. Thus, C = 100 + 10h 
Option 2: C = 15h 

b) How many hours for cost of option 1 to be less than cost of option 2? 

{{{ 100 + 10 h < 15 h}}} 

Subtract 10h from both sides: 

{{{ 100 < 5 h}}} 

Divide both sides by 5 to get: 

{{{ 20 < h }}} 

that is, option 1 is cheaper when the temp works more than 20 hours  {{{h > 20 }}}.