Aconsumer charges a $2,530.16 purchase on their credit card. the card has a daily interest rate of 0.042%. if the consumer pays off the balance at the end of 30 days, how much more in interest will they pay for the purchase?
a. $0.32
b. $3.19
c. $31.88
d. $318.78

Amount after interest = original amount x (interest rate)^(time)
Amount after interest = 2,530.16 x 1.00042³⁰
Amount = $2562.23

Interest = 2,562.23 - 2,530.16
= $32.07

The answer is C.

The equation that we need to use to answer the question above is,
                           I = P x ((1+r)^t) - P
where P is the principal amount, r is the interest rate (in its decimal equivalent) and t is time. Substituting the known values from the given,
                          I = ($2,530.16) x ((1 + 0.042/100)^30) - $2,530.16 
                                 I = $32
The nearest answer should be letter C. 

$18.25 ($365 divided by 20)