Use MATH-WAY it has all the answer
The cost should be the same on day 3
we have

the solution is the interval -------> (3,∞)
therefore
the answer in the attached figure
Answer:
i only understand part A:
a) Yes, the more time the plant spend in sunlight, the taller it grows. for example, the plant that spend no time in the sun only grows to 4cm while the plant that spent 9 hours in the sun grew to 31