a) For a firm, how does the concept of producer surplus differ from that of profit if it has no fixed costs?

a) For a firm, how does the concept of producer surplus differ from that of profit if it has no fixed costs? 

b) If the inverse demand function for toasters is: p = 60 - Q

What is the consumer surplus when the price is 30?

c) The inverse demand function a monopoly faces is: p = 100 - Q

The firm's cost curve is: C (Q) = 10 + 5Q

What is the profit-maximizing solution?