A father wanted to show his son what it might be like to borrow money from a financial insitution. When his son asked if he could borrow $120 the father lent him the money and setup the following arrangements:

He charged his son $6 for the loan of $120.

Therefore the son received $114 and agreed to pay his father 12 installments of $10 a month, beginning one month from today,until the loan was repaid.

Find the approximate rate of simple interest the father charged on this loan.

Please show some work

Thanks a ton!