The demand function for a certain brand of compact discs is given by p = -4x2 - 3x + 78 where p is the wholesale unit price in dollars and x is the quantity demanded each week, measured in units of a thousand. (a) Compute the price, p, when x = 4. Price, p = dollars (b) Use implicit differentiation to compute the rate of change of demand with respect to price, p, when x = 4. Do not round your answer. Rate of change of demand, x' = thousands of units per dollar (c) Compute the elasticity of demand when x = 4. Do not round your answer. Elasticity of Demand =