people will be able to be fed at the time the world's population has doubled?

The bulk of human food is provided by eight grains (wheat, rice, corn, barley, oats, sorghum, millet and rye). Current world grain production is about 1.54 Billion metric tons, which is enough to feed about 7.96 Billion people. Assume for the sake of this problem that grain is the only food we eat. If the world's production of food is increasing linearly at about 1.3% per year and the population is growing at 1.3% per year, how many people will be able to be fed at the time the world's population has doubled? Your answer will be x billion people, so in the answer box only enter the x value. So for example, if you calculate 20 billion people, enter 20 in the answer box. Round your answer to ONE place past the decimal.
Able to be fed (in Billions) =