The quantity demanded of a certain brand of smartphone is 2000 per week when the unit price is $84. For each decrease in unit price of $5 below $84, the quantity demanded increases by 50 units. The supplier will not market any of the smartphones if the unit price is $60 or less, but the supplier will market 1800 per week if the unit price is $90. The supply equation is also known to be linear.
a. Find the demand and supply equations.
b.Find the equilibrium quantity and price.