Abusinessman models the number of items (in thousands) that his company sold from 1998 through 2002 as n(x) = −0.2x3 + x2 − 2x + 9 and the average price per item (in dollars) as p(x) = 0.6x + 5, where x represents the number of years since 1998. enter a polynomial r(x) that can be used to model the total revenue for this company.

Basically, you are asked to find the equation for total revenue. In economics, total revenue is equal to the the quantity multiplied with price.

Total Revenue = Price*Quantity
Thus,
R(x) = P(x) * N(x)
R(x) = (0.6x + 5)(−0.2x³ + x² − 2x + 9)
R(x) = -0.12x⁴ + 0.6x³ - 0.12x² + 5.4x - x³ + 5x² - 10x + 45
R(x) = -0.12x⁴ - 0.4x³ + 4.88x² - 4.6x + 45