I'm having trouble with the following:

An international organization must decide how to spend the $2,000 they

have been allocated for famine relief in a remote area. They expect to

use the money to buy rice at $5 per sack and beans at $10 per sack.

The number P, of people who would be fed if they buy x sacks of rice

and y sacks of beans is given by

$\displaystyle P = x + 2y + \frac {x^2y^2}{2*10^8}$

What is the maximum number of people who can be fed and how much

of each food should the organization purchase?

Thanks.