Although Earth's atmosphere is stratified, there is still exchange of air between, for example, troposphere and stratosphere. In the following, consider only the stratosphere and the troposphere. The lifetime of air in the stratosphere is 1.72 years. Determine the lifetime of air in the troposphere in years. Assume that the troposphere extends to 15.0 km in height and that the stratosphere extends from 15.0 km to 50.0 km. The molar mass of air is 28.96 g/mol. Assume a temperature of 15.0 °C.