HELP PLEASE, MATRICES IN MATH?

A company makes three kinds of engineering pencils, Type I, Type II, and Type III and uses two machines, a sander and a polisher. Each type I pencil needs 3 min of sanding and 5 min of polishing. Each type II pencil needs 2 min of sanding and 4 min of polishing. Each type III pencil needs 9 min of sanding and 5 min of polishing. The sander can run no more than 132 hours per week and the polisher can run no more than 159 hours a week. How many pencils of each type can be made each week if the two machines are fully utilized and if the number of type I pencils is to be twice the number of type III pencils?