Original practice · fully worked
Original variant: monthly payment under continuous card interest and fees
A card is charged 1,000 immediately, charges a fee of 15 at each year-end, and uses a 12% annual force of interest. Equal payments occur at the end of each month for two years and leave zero balance at year 2. Determine the monthly payment.
- A
38.28 - B
43.28 - C
48.28 - D
53.28 - E
58.28
Answer and calculation
Discounting the initial charge, two fees, and 24 payments at monthly force 0.01 gives X = 48.28, choice C.
Setup
Setup
Value all card charges and payments at the card-opening date.
1000+15e−0.12+15e−0.24=Xk=1∑24e−0.01k Model
Model
Monthly payments discount with exponent 0.01 per month, while fees occur at years one and two.
k=1∑24e−0.01k=21.230706 Compute
Compute
Dividing the charge value by the 24-payment discount sum gives 48.28399.
X=48.28399 Answer
Answer
The monthly payment is 48.28, corresponding to choice C.
X=48.28(C)