When a minimum wage frustrates the market mechanism, at the quantity of labour employed
A. firms' marginal social benefit of using labour exceeds workers' marginal social cost of supplying labour.
B. the sum of the firms' surplus from labour and the workers' surplus from labour is minimized.
C. firms' marginal social benefit of using labour is less than workers' marginal social cost of supplying labour.
D. the firms' surplus from labour exceeds the workers' surplus from labour.
E. the firms' surplus from labour is less than the workers' surplus from labour.