A car dealership estimates that the total weekly sales of its most popular model are a function of the car's list price p (in dollars) and the interest rate i (as a percent) offered by the manufacturer. The weekly sales are given by the equation below. Complete parts (a) through (c). f(p,i) = 98p 0.7pi 0.0026p2 (a) Find the weekly sales if the average list price is $19,000 and the manufacturer is offering a 5% interest rate. The weekly sales would be $ 856900 . (b) Find and interpret fp(p,i) and fi(p,i). fp