Which of the following equations could represent the account balance … | Math SAT Question

A certain investment account offers a special interest rate for the first

4

months the account is open followed by a lower interest rate for the remainder of the time the account is open. Bennett opened one of these accounts with an original account balance of $700 and did not make any other deposits or withdrawals.

4

months after Bennett opened the account, the balance had increased by

0.6%

of the original balance.

6

months after Bennett opened the account, the balance had increased by an additional

0.2%

of the balance at the end of the first

4

months. Every

2

months after the first

6

months, the balance had increased by an additional

0.2%

of the balance

2

months before.

Which of the following equations could represent the account balance

B (x)

, in dollars,

x

months after the account was opened, where

x \geq 4

B (x) = 704.20 (1.002)^{\frac{x - 4}{2}}

B (x) = 704.20 (1.002)^{\frac{x}{2} - 4}

B (x) = 704.20 (1.002)^{2 x - 8}

B (x) = 704.20 (1.002)^{2 x - 4}