Explanation and Answer please.

There are 100 identical firms in a perfectly competitive industry. The cost to each firm in the industry of producing output y is 1/2 y". The industry demand for the good as a function of its price is Q=1200-20p. a. (4 pts) Assume that firms cannot enter or leave the industry. Find the price of the good and the quantities produced by each firm, and the entire industry. How much profit does each firm make? b. (2 pts) Assume now that firms can enter the industry but in order to do so they have to obtain a health and safety certificate. This costs 60. There are 500 potential entrants. How many enter the industry? C. (4 pts) How many firms would enter the industry if the certificate costs 8