Your friend has two investment opportunities that she is considering and has asked for your advice regarding how she should proceed. One will have an 7.0% rate of return on an investment of $510; the other will have a 9.0% rate of return on an investment of $630. She would like to take advantage of the higher-yielding investment but has only $510 available.

Required:

What is the maximum rate of interest that your friend should be willing to pay to borrow the $120 needed to take advantage of the higher yield?