4. Adding curves Alan, Barbara, and Charlie have the following individual demand curves for ball bearings. Alan: Q = 30 P Barbara: (1: 20 P Charlie: Q = 5/2 1/2 P 3) Write out the expression that represents the market demand curve and plot it on a graph. b) The market supply is given by Q = 3P. Calculate the market equilibrium and plot it on the graph. c] Calculate consumer surplus and producer surplus