Watson electric has production facilities in valley mills, marlin, and hillsboro. each one produces radios, stereos, and tv sets. their production capacities are as follows. valley mills: 12 radios, 10 stereos, and 6 tv sets per hour marlin: 6 radios, 10 stereos, and 6 tv sets per hour hillsboro: 4 radios, 3 stereos, and 12 tv sets per hour let x1 = hours at valley mills, x2 = hours at marlin, x3 = hours at hillsboro.