Which one of the following is correct about the yield to maturity on a bond?

a) YTM is below the coupon rate when the bond sells at a discount, and equal to the coupon rate when the bond sells at a premium

b) YTM is the discount rate that will set the present value of the payments equal to the bond price

c) YTM is based on the assumption that any payments received are reinvested at the coupon rate

d) YTM is always equal to the coupon rate.