Suppose There Is a Competitive Market for Retail Workers at a Large

Suppose there is a competitive market for retail workers at a large shopping mall that is large enough to constitute its own labour market.The labour demand curve is Q_D = 1000 - 20(w) .The labour supply curve is Q_S = 400 + 40(w) .Suppose that a union now successfully organizes the workers at this mall and obtains a wage rate of $11 (but does not affect the demand curve) .The number of unemployed workers in this mall labour market becomes

A) 20.
B) 40.
C) 60.
D) 80.
E) 100.