What is the probability that a value falls in the interval μ ± 2σ, that computes the probability p(-2 < z < 2). round to four decimals and use leading zeros

Suppose that the price p, in dollars, and the number of sales, x, of a certain item follow the equation 4 p plus 4 x plus 2 pxequals56. suppose also that p and x are both functions of time, measured in days. find the rate at which x is changing when xequals2, pequals6, and startfraction dp over dt endfraction equals1.5.