A vertical tube is filled with mercury of density 13600kg/m^3.find the height in millimeters of the column of mercury? Please help

The number of passengers who arrive at the platform of a subway station for the 10 am train is a random variable with a mean of 120 and a variance of 16. find the lower bound of the probability that there will be between 100 and 140 passengers (round off to second decimal place).