We let the price or cost of Brand A be x and Brand B be y
a) The cost of brand A is P26,000 and brand B is P16,000
b) Brand A - P26,000*0.12= P3,120
Brand B- P16,000*0.8= P1,280
c) I will sell brand A to maximize my savings since it has higher commission. And of course you would let your clients buy brand A since it has higher commission for you.