DERIVATION OF BRICK COMBINATION FORMULA FOR CEMENT KILN

HOW CAN I DRIVE THIS FORMULATION FOR BRICK RATION CALCULATION IN CEMENT KILN?

IN KILN BRICKS COMBINTION IS ONLY FOR TWO TYPES BUT IF WE HAVE THREE OR FOUR TYPES OF BRICKS HOW CAN  WE DRIVE SUCH FORMULA?

PLEASE POST COMPLETE DERIVATION SHEET

THANKS

SIDDHANT