Talia took out a loan to pay for textbooks. At the end of a year, Talia has to pay back the full loan amount, a plus interest. • Interest is calculated as 21% of the original amount.

• Talia paid a total amount
of $506 at the end of the year, including interest.
Which of the following equations can help you solve for the original loan amount, a?

A. 506 = 1.21a
B. 0.79a = 506
C . 506 = 21a
D. 0.21 + a = 506