Flight is $295 and car rental is $39 a day, if a competition charges $320 and $33 a day car rental, which is cheaper? Set up cost function where d is the number of days: Control business: C(d) = 39d + 295 Competitor business: C(d) = 33d + 320 Set the cost functions equal to each other: We get d = 4.1667. The next integer day up is 5. Now plug in d = 1, 2, 3, 4. For the first 4 days, the control business is cheaper. However, starting at day 5, the competitor business is now cheaper forever.