A mathematical model for world population growth over short intervals is given by P = Poet, where Po is the population at time t = 0, r is the continuous compound rate of growth, t is the time in years, and P is the population at time t. How long will it take the world population to double if it continues to grow at its current continuous compound rate of 1.05% per year? Substitute the given values into the equation for the population. Express the population at time t as a function of Po Po-Poe (Simplify your answers.) The population will double in about years. (Type an integer or decimal rounded to one decimal place as needed.)