A spherical balloon initially contains 25m3 of helium gas at 20ºC and 150kPa. A valve is now opened and the helium is allowed to escape slowly. The valve is closed when the pressure inside the balloon drops to the atmospheric pressure of 100kPa. The elasticity of the balloon material is such that the pressure inside the balloon during the process varies with volume according to the relationPabV=+, where a = -100kPa and b is a constant. Disregarding any heat transfer, determine: a) The final temperature in the balloon b) The mass of helium that has escaped.