If the Demand for the Weekly World News at a Local

If the demand for the Weekly World News at a local grocery store is described by Q = 2,500 - 400P - for I = $15,000 and P = $1.50, the marginal revenue of an additional paper sold at this store is

A) $.15.
B) $.38.
C) $.50.
D) $1.50.
E) $1.