Please guys help me with two of these problems Thank u so much

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?

For a gate width of 2 m into the paper, determine the force required to hold the gate abc at its location.

When subject to a steady load (within elastic range) over a long period of time, what is the major difference in material behavoir between steel and plastic?