Exercise 7.1.4 Sketch the level curves of the function corresponding to the given values of z. (a) f(x,y) = 3x + 2y, z= -2, -1,0, 1,2 (b) f(x,y) = x- y, z=-2, -1,0,1,2Exercise 7.1.5 A clothing retailer sells casual and business jackets. Let qc denote the quantity of ca- sual jackets demanded monthly and qb denote the quantity of business jackets demanded monthly. It is determined that the unit price of casual jackets is approximately Pc = 100 - 79c - = qb, and that the unit price of business jackets is approximately Pb = 150 109c 39b dollars, respectively. (a) Determine the monthly revenue, R(qc, qb). (b) Determine the domain of R.