Need help please:

Using the unpaid balance method, find the current months finance charge on a credit card account having the following transactions.
Last months balance: $420
Last payment: $140
Annual interest rate: 15%
Purchases: $636
Returns: $852

Use the simple interest formula I=Prt.
The finance charge is blank. Round to the nearest cent

Need help please Using the unpaid balance method find the current months finance charge on a credit card account having the following transactions Last months b class=