A 3-m³ tank is in the basement of your house to store propane that will be used for home and water heating and cooking. Your basement, and therefore the contents of the tank, remain at 20°C all year. Initially, except for a small vapor space the tank is completely full of liquid propane, but by January 60 percent of the propane has been used. Compute 

a. The fraction of the remaining propane that is present as vapor 

b. The total flow of heat into the tank over the period in which the propane has been used