Concrete blocks are produced by thousands of small producers in a perfectly competitive market. Each producer faces total costs of TC=Q^3-6Q^2+20Q+300 , where Q is the quantity of blocks, in hundreds. The corresponding marginal cost curve is given by MC=3Q^3-12Q+20 .

a.What is the average variable cost of production?

b.What is the marginal cost of production?

c.What is the minimum price sellers must receive if they are to produce any concrete blocks at all?