The Period at the End of This Sentence Has an Area

The period at the end of this sentence has an area of approximately 0.2 mm².One carbon atom,having a diameter of about 160 pm,covers an area of about 0.02 nm².How many carbon atoms would be required to produce a one-atom-deep layer that covers 0.2 mm²?

A) 1 * 10¹²
B) 2 * 10¹¹
C) 1 * 10⁷
D) 1 * 10¹³
E) 2 *10⁶