Elvie can encode a document 4 hours more than EJ does. The two worked together in 3 hours when EJ left for an important appointment. Elvin continued the job and completed it in two hours.

Ahe-xe mixture containing a 0.75 mole fraction of helium is used for cooling electronics in an avionics application. at a temperature of 300 k and atmospheric pressure, calculate the mass fraction of helium and the mass density, molar concentration and molecular weight of the mixture. if the cooling capacity is 10 l, what is the mass of the coolant?