Can someone please explain why a) and c) is FALSE?

A5 Demand in a competitive market is Q = 20 0.5P. The private marginal cost of all producers in this market is 10, the social marginal cost is 5. '1' 85111 the absence of any interventions, production in this market is inefficiently high? (b) The solution to the external effect present in this market is to have a cap on the amount? produced in this market and to allow producers to trade freely their quotas. / 4 Q The deadweight loss in the case of no intervention is larger than 100. F