The world carbon emissions can be expressed by the following equation: Carbon emissions = (population)x(energy/person)x(carbon/energy) Energy/person grows at 2.4 %/year World population grows at 1.4 %/year Fossil fuel emissions of carbon per unit of energy increase at 1.4 % /year Assuming constant exponential growth, how long would it take (in years) to reach 4 times of initial carbon concentration (N/No = 4)?