Final answer:
The revenue function for the supply company charging for 90-gallon tanks is R(x) = (20.6 - 1.9x) * x.
Step-by-step explanation:
The revenue function can be found by multiplying the price per gallon by the quantity of gallons sold. In this case, the demand function is given as p(x) = 20.6 - 1.9x. The price per gallon is represented by p(x). To find the revenue function, we multiply the price per gallon by the quantity of gallons sold. Let x be the number of 90-gallon tanks sold. Therefore, the revenue function is given by:
R(x) = p(x) * x
Substituting the demand function into the revenue function, we have:
R(x) = (20.6 - 1.9x) * x
This is the revenue function for the supply company charging for 90-gallon tanks.