You need to multiply 13.4 by 5,880,000,000,000.
First, we change both numbers into scientific notation.
13.4 = 1.34 * 10^1
5,880,000,000,000 = 5.88 * 10^12
Now we multiply the numbers written in scientific notation.
1.34 * 10^1 * 5.88 * 10^12 =
= 7.8792 * 10^13
The answer is choice A.