Please help with the following problem that involves systems of linear equations.
A cookie company makes three kinds of cookies, peanut butter, sugar,and oatmeal packaged in small, medium, and large boxes. The small box contains 1 dozen peanut butter and 1 dozen sugars; the medium box contains 2 dozen peanut butters, 1 dozen sugars, and 1 dozen oatmeal cookies; the large box contains 2 dozen peanut butter, 2 dozen sugars, and 3 dozen oatmeal. If you require 15 dozen peanut butter, 10 dozen sugars and 11 dozen oatmeal cookies, how many of each size box should you buy?