2 g of a gas A are introduced into an evacuated flask kept at 25∘C. The pressure is found to be 1 atm. If 3 g of another gas B are added to the same flask, the total pressure becomes 1.5 atm. Assuming ideal gas behaviour, calculate :
a. the ratio of molar masses of MA and MB .
b. the volume of the vessel, if A is O2 .