Danno is trying to decide which of two bonds to buy. Bond H is a 10 percent coupon, 10-year maturity, $1,000 par, January 1, 2000 issue paying annual interest. Bond F is a 10 percent coupon, 10-year maturity, $1,000 par, January 1, 2000 issue paying semiannual interest. The market required return for each bond is 10 percent. When using present value to determine the prices of the bonds, Danno will find that .

Combining the emissions released by fossil fuel burning and  the carbon released via land use change, we get a total of 8.7 gt. since the problem states that the oceans "take up" or sequester  2.4 gt carbon  per year, we subtract that value from 8.7 gt, leaving us with 6.3 gt of carbon. since the problem states that 3.4 gt carbon dioxide emissions end up in the atmosphere, the "missing sink" of carbon takes up 2.9 gt, a value we got by subtracting the 3.4 gt amount recorded from the 6.3 gt carbon left available after the oceans sequester the carbon dioxide. 

You add 625.84 to 640.31 and the sum is 1266.15. got it right on edgenuity.