Are the following statements true, false Please give an explanation 

(a) Although a prot maximizing rm in a competitive industry may earn negative prots in the short run, producer surplus will always be nonnegative.

(b) For a given technology and input prices, the long run average and marginal costs are always below the short run average and marginal costs (respectively) for any level of output.

(c) Long run market supply curves are always at at prices equal to minimum average.