The costs of publishing a grade school textbook can be assumed to be as follows.

Fixed expenses for each new edition of the book:

Copy editing $3,000

Art work $1,000

Typesetting $36,000

Variable expenses per copy of the book:

Printing and binding $1.60

Bookstore discounts $2.00

Salespersons' commissions $0.25

Author's royalties $1.00

Each book sells for $10 per copy.

The unit contribution margin for each copy of the book is:

A. $5.15

B. $4.15

C. $5.40

D. $7.15