15 ) the demand function for a certain commodity is P= - 1. 502- 60 +110 where p isthe unit price in $ and a is the quantity demanded each month 9 / if the unit is set at$ 20 show that x= 6 by solving forx, the number of unit sold, Not by plugging De = 6 b/ Find the consumers' semplus if the selling price is set at $20. use x = 6