1. A TRUST INVESTED MONEY IN TWO TYPES OF BONDS. THE FIRST BOND PAY 10% INTEREST AND SECOND BOND PAYS 12% INTEREST. THE TRUST RECEIVES  2800 AS INTEREST. HOWEVER, IF TRUST HAD INTERCHANGED MONEY IN BONDS THEY WOULD HAVE GOT 100 LESS AS INTEREST. USE MATRIX METHOD TO FIND THE AMOUNT INVESTED BY THE TRUST.