Environmental chemistry - change in carbon

The total mass of Carbon contained in fossil-fuels that were burned in the world from the year 1750 to the year 2000 was estimated to be 2.7 x E14 kg C. The amound of carbon released as CO2 from agricultural expansion and deforestation over this period is estimated to be 1.3 x E14 kg C. The concentration of CO2 in the atmosphere in 2000 was 360 ppm, corresponding to a total mass of 7.75E14 kg C. If the concentration of carbon dioxide in 1750 was 250 ppm, calculate the percentage of carbon dioxide from these two sources that remained in the atmosphere over the two and one-half century period.

(b) Plant studies indicate the net primary production (NPP) of organic carbon by photosynthesis may increase with increasing CO2 concentration in the atmosphere. Assume the increase of NPP in the biosphere is 0.31 of the percentage increase of atmospheric CO2. Given that the global NPP of the biosphere is currently estimated to be 1.1E14 kg C/yr, estimate how much more carbon (kg C) is being absorbed per year in the NPP compared to the amount that would be abosrbed if the atmospheric CO2 concentration was the same as in 1750.