To sell 300 notebooks and 120 pens quickly, a store decided to create two types of gift sets. One set is to include 2 notebooks and 1 pen, and the other will consist of 1 pen and 3 notebooks. The first set will be sold for $8, while the second will be sold for $11.50. It is unprofitable to sell more than 20 of any gift set. How many gift sets of each type must the store sell to obtain the biggest possible income?