Susan makes a purchase of $175 and is charged 7.75% for sales tax. what is the total cost of the purchase if susan charges it on a credit card with a daily interest rate of 0.039% and pays the balance off at the end of 30 days?

a. $176.17

b. $186.70

c. $190.77

d. $200.26

The answer Is C. Just took the quiz :)

Solve first for the total cost of the item with tax.
Total cost= item +sales tax
                = $175(1+.0775)
                 = $188.56
Use simple compunding interest formula
where
i= .00039 or 0.39%
n=30
Present worth=$188.56

Total cost of the item if charged on credit card= 188.56(1+0.00039)^30
                 = $190.77The total cost of the item if charged on the credit card and paid at the end of the month is $190.77.