An investor owns a bond that is redeemable for 300 in seven years. The investor has just received a coupon of 22.50 and each subsequent semiannual coupon will be X more than the preceding coupon. The present value of this bond immediately after the payment of the coupon is 1050.50 assuming an annual nominal yield of 6% convertible semiannually.

Calculate X. I do not understand how to know at what time the investor recieved the coupon of 22.50 , if that is included in the fourteen semiannual payments?