Trouble with Basic Math Formula *(Updated)?

Question

have this question for a chem class. Here is the question.

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 1.8 Billion metric tons, which is enough to feed about 8.1 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 1.4% per year, how many people will be able to be fed at the time the world's population has doubled?
A. 10.0 Billion
B. 14.2 Billion
C. 620 Billion
D. I think it should be more than 12 Billion, but I don't get answer B or C

E. I think it should be less than 12 Billion but I don't get answer A

The doubling time is 50 years. Now I have a formula that gave me how much food will be produced. The answer is 3,060,000,000. Now I need to figure out how to convert that to how many people that number can feed. Any ideas? Thaaanks.

Answer 1

16.23 billion people. Each year the production rate increases by a factor of 1.014. In 50 years you have an increase of 1.014^50, almost exactly 2, pretty well tracking the population growth rate. (Look up the "rule of 70" some time.) This means
1.014^50 * 8.1 bil = 16.23 bil people fed, or
1.014^50 * 1.8 bil = 3.607 bil tonnes.