Answer: 0.8015
Step-by-step explanation:
Let F= event that a person has flu
H= event that person has a high temperature.
As per given,
P(F) =0.35
Then P(F')= 1- 0.35= 0.65 [Total probability= 1]
P(H | F) = 0.90
P(H|F') = 0.12
By Bayes theorem, we have

Required probability = 0.8015
Multiply number of gallons by 16 (because 16 oz/ 1 gallon).
29.98+ 6.44 = 36.42 (cost with out the discount)
36.42/3 = 12.14
Answer-
12.14