What is the temperature of o3 gas if the average speed(actually the root mean square speed of the molecules is 750 m/s

How much would the freezing point of water decrease if 4 mol of nacl were added to 1 kg of water (kf=1.86 degrees c/(mol/kg) for water and i=2 for nacl a- 7.44 degrees c b- 14.88 c 3.72 d 1.86