Interview To Obtain Response From Households With Children

Hello, I’m stuck answering the minimization problem below: Market Survey Inc (MSI) specializes in evaluating consumer reaction to new products. A client has recently asked MSI to conduct 1000 door-to-door personal interviews to obtain response from households with children and households without children to a new product. MSI can do both day and evening interviews with the following costs per interview: Day Evening Children $20 $25 No Children $18 $20 In addition, the following quota guidelines are required by the client: 1- Interview at least 300 evening interviews 2- At least 40% of the day interviews must be from households with children. MSI should now determine the best household, time-of-day interview plan that minimizes interview costs. Develop a spreadsheet and find the optimal number of interviews of each type. ***break**** This is what I have so far: Decision Variables DC = # day interviews of households w/ children EC = # evening interviews of households w/ children DNC = # day interviews of households w/out children ENC = # evening interviews of households w/out children Objective Function Minimize 20DC + 25EC + 18DNC + 20ENC Contraints DC + EC + DNC + ENC = 1000 EC + ENC ≥ 300 -0.4EC + 0.6DC ≥ 0 Nonnegativity: DC, EC, DNC, ENC ≥ 0 LP Model: Min 20DC + 25EC + 18DNC + 20ENC DC, EC, DNC, ENC ≥ 0 DC + EC + DNC + ENC = 1000 Total Interviews EC + ENC ≥ 300 At Least 300 Evening Interviews 0.6DC – 0.4EC ≥ 0 Day Interviews in Households w/ Children *I am having problems setting this up in excel solver. Please help!