In the value of bonds, the symbol "M" means "thousands. Therefore, 10 M = 10,000$
So, the customer bought a coupon with 10,000$ and the expected annual interest is 7.5% of the coupon's value.
Calculating the value of interest is simple, just multiply the interest rate (7.5%) by the original value of the coupon to know how much interest she will collect each year.
Interest collected each year = (7.5 / 100) x 1000 = 750$
