The demand, D, for a new rollerball pen is given by D=0.007p30.8p2+140p, where p is the price in dollars a) Find the rate of change of quantity with respect to price, dD/dp. b) How many units will consumers want to buy when the price is $25 per unit? c) Find the rate of change at p=25, and interpret this result. d)Would you expect dD/dp to be positive or negative? a) dpdD=.