Suppose that the price p, in dollars, and the number of sales, x, of a certain item are related by 6p + 4x + 2px = 86. If p and x are both functions of time, measured in days. Find the rate at ap which x is changing when x = 4, p =5, and = 1.8. dt The rate at which x is changing is (Round to the nearest hundredth as needed.)