Suppose Megabox is a new case designed for smartphones. We know its demand curve and supply curve as below. Here the units of P and Q are, P: $/case, Q: thousand cases.

• Demand function: Q_d = 100 - 2 * P
• Supply function: Q_s = -20 + 4 * P

(1) How much is consumer surplus (CS) when Megabox is priced at $35 in the market?

(2) How much is consumer surplus (CS) when price the case drops to $25?

(3) How much is consumer surplus (CS) at market equilibrium price of Megabox?

(4) How much is producer surplus (PS) and total surplus (TS) at market equilibrium?