Concept:Revenue per shop = sum of (quantity of each product × price) obtained by matrix multiplication.Explanation:Let sales matrix S=[800600​600500​400400​100200​].Let price vector P=​10203040​​.Monthly revenue R=S×P, a 2×1 matrix.Shop I: 800×10+600×20+400×30+100×40=8000+12000+12000+4000=36000.Shop II: 600×10+500×20+400×30+200×40=6000+10000+12000+8000=36000.Answer:Shop I = Rs. 36000, Shop II = Rs. 36000.