A40-l electrical radiator containing heating oil is placed in a 50-m3 room as shown in the figure. both the room and the oil in the radiator are initially at 10°c. the radiator with a rating of 2.4 kw is now turned on. at the same time, heat is lost from the room at an average rate of 0.35 kj/s. after some time, the average temperature is measured to be 20°c for the air in the room, and 50°c for the oil in the radiator. taking the density and the specific heat of the oil to be 950 kg/m3 and 2.2 kj/kg·°c, respectively, determine how long the heater is kept on. assume the room is well-sealed so that there are no air leaks. the gas constant of air is r = 0.287 kpa. m3/kg. k. also, cv = 0.718 kj/kg. k for air at room temperature. oil properties are given to be ρ = 950 kg/m3 and cp = 2.2 kj/kg.°c. (round the final answer to one decimal place.)