To answer this question you must find how much she will pay if she uses her credit card vs using an loan. She wants to pay it of in 6yrs in one yr there are 12 monthes so in 6 yrs that is 72 months, which is 72 payments. So you do 220 times 72 which=15840 total, that is how much total she will pay if she uses her credit card. If she uses a lone do 180x72=12960.
If she uses an credit card she will pay $2880 more dollars
Pretty positive this is right hope it helps ^^