I need help with this problem.

Jason's credit cards beginning unpaid balance for August is $2,000. During the August billing cycle he made a payment of $200 and used card to purchase $50 worth of groceries. Credit card charges 24% annual percentage rate and uses the unpaid balance method.

a) What is the finance charge at the end of August?

b) What is the new balance at the end of August?

a. Bal. = 2000 - 200 + 50 = 1850.

Int. = 0.24(31/365) * 1850,
Int. = 0.02038 * 1850 = 37.71.

b. New Bal. = 1850 + 37.71 = 1887.71.

NOTE: Some companies use 360 days as a business year.