A supermarket sells tow brands of granola: brand A at Sp per pound and brand B at Sq per pound. The daily demands x and y (in pounds) for brand A and B, respectively are gives by the following equation. x= 200 - 9p + 6q y = 400 + 6p - 3q Find partial differential x/partial differential p and partial differential y/partial differential p. and interpret the results. partial differential x/partial differential p = (Enter your response as a whole number and include a minus sign if necessary)