added failing test for Calculator.new(100).benefit_hvac when hvac is not included
added passing code for Calculator.new(100).benefit_hvac when hvac is not included
added passing code for Calculator.new(100).benefit_hvac when hvac is not included
added failing test for Calculator.new(100).benefit_hvac when hvac is included
added passing test for Calculator.new(100).benefit_hvac when hvac is included