A solution is made by mixing 1 mole benzene ( = 100 mm Hg) & 1 mole toluene ( = 40 mm Hg).Suppose, initially the pressure over the solution is very high so that no vapour exist above the liquid. As we gradually decrease the pressure, a point (bubble point) comes when we aross the bubble point curve & first bubble of vapour starts forming (hence called bubble point curve). Now we have entered the vapour-liquid equilibrium region. On further decreasing the pressure, a point (dew point) comes when we cross the dew point curve then almost all the liquid has evaporated into vapour i.e. only the last drop of liquid (dew) remains. Beyond this point no liquid exist in the system. Then answer the following questions :

(i) If the pressure over the mixture at 300 K is reduced, at what pressure does the first bubble form :