Hello. I am having difficulties understanding the applied aspect of macroeconomics. Please help me understand it further. Here is the situation:

A country has a real capita income of 3850 US Dollars.

If the country is able to sustain the average increase in real GDP to 6% per year and a population of 2% in growth per year, how many years will it take for this per capita income to double to 7700 US Dollars?

If the average increase in real GDP goes down to 2% per year and the population grows at 3%, how many years will it take for per capita income to double?

Along with the computations, may you also help me explain why the answers are the way they are through in-depth explanations?

Thank you tutor.