Hongyi is now studying population growth The population of sub-Saharan Africa is projected to almost double in size in the coming decades Suppose that the rate of change of population in Somalia is always proportional to Somalia's population: a! = . a: k viti where ym is Somalia's population at time t and k is the population growth rate. In 2017, the population was 1&4 million Four years later, Somalia's population was 17.9 million. At the current rate ot change, how long (in years) after 2017 will it take for the country's population to double [to 321-} million)? years