Appartment B is cheaper. Explanation: we need to compare these two values. A = 600 and B = 400 + cost of heat per month + cost of electricity per month. The cost of heat per year is 800, which gives us a monthly cost of 800/12 = ~$67. So the rent cost for appartment B is 400 + 40 + 67 or 507, which is less than 600.