Total Cost in a day is

. Profit function is

. And the revenue function is

. In a day, bookstore must sell at least 15 books, because of 6n-90=0, in order to make profit.
There are several information's already given in the question. based on those information's, the answer can be easily determined.
Height of the box = h cm
Length of the box = 10 cm
Width of the box = 2h
Then
Volume of the box = Length * height * width
= 10 * h * 2h cubic cm
= 20h^2 cm^3
I hope that the above procedure is clear enough for you to understand and it has actually come to your desired help.
Step-by-step explanation:
first way by sitting 3 person in one chair
F(n) = 75*1/5n
This is because the base value would be 75 and it is divided by 5 each part of the sequence.