You like the size of your MP3 player. The width is 4 centimeters. The length is 7 centimeters. The height measures 1 centimeter. What is the surface area of your MP3 player, in square millimeters?
A. 39 square centimeters
B. 78 square centimeters
C. 3,900 square millimeters
D. 7,800 square millimeters