If the marginal social cost of producing a ton of cement is $4,000 and the marginal private cost is $3,500, then the

A) marginal benefit of a ton of cement will equal $4,000.
B) total cost of producing a ton of cement is $7,500.
C) marginal external cost of producing a ton of cement is $500.
D) marginal external cost of producing a ton of cement is $7,500.
E) marginal external cost of producing a ton of cement is $4,000.

C