Answer:
Since the total amount you have to pay for the purchase on the credit card A is lower, then it's the best option.
Explanation:
For credit card A the ammount will only be compounded after 1 year, so the total time elapsed for the laon is 1.5 years, while for the credit card B it'll be the full 2.5 years. To compute the total amount of a interest compounded continuously we must apply the formula:
M = C*e^(r*t)
Where M is the total amount, C is the initial amount, r is the interest rate and t is the time elapsed.
For credit card A:
M = 500*e^(0.008*1.5) = 506.03614
For credit card B:
M = 500*e^(0.007*2.5) = 508.8270
Since the total amount you have to pay for the purchase on the credit card A is lower, then it's the best option.