Vince borrows $900 to buy a couch. He will pay off the loan by paying 15% simple interest for 2 years. Vince incorrectly calculates the amount he will pay back using the expression below: 900(1 + 15 * 2). What is the correct amount Vince will pay back altogether? Explain the error in Vince's expression.
a. $1,260
b. $1,170
c. $1,035
d. $990