The supply curve of a commodity is given by the equation :

Qs = 40P – 60 (P is measured in $, Q is measured in millions of units)

A fall in demand caused by increased availability of substitutes for consumers leads to a fall in the market price of this commodity from $6 to $4.

The loss in producer surplus for the producers of this commodity from the change is:

A. $ 280m

B. $ 160m

C. $ 140m

D. $80 m    

Explain your answer.