SSP Cafe sells coffee and breakfast. Its related products include coffee, sandwich and cake. The sale proportion between coffee and sandwich is 5 : 2, while those for between coffee and cake is 15 : 3. The following are details of these three products. Cost of coffee 60 Baht per unit Cost of sandwich 25 Baht per unit Cost of cake 40 Baht per unit Commission cost 5 Baht pe runit Rent 244,400 Baht per month Packaging for coffee 10 Baht per unit Packaging for sandwich 5 Baht per unit Packaging for cake 4 Baht per unit When coffee, sandwich and cake prices are 150 Baht per unit, 70 Baht per unit and 90 Baht per unit, respectively, what is the break-even point of coffee for a quarter