A Monopolist Faces a Straight- Line Demand Curve and Is

A monopolist faces a straight- line demand curve and is currently producing an output level of 2000 units receiving $10 000 in total revenue. At an output of 1 000 units the marginal revenue for this firm would be

A) 0.
B) $2.50.
C) $5.00.
D) $10.00
E) impossible to tell with the given information.