finance internal growth rate, sustainable growth rate, debt to equity ratio

1) What is the internal growth rate?
2) Given your calculated internal growth rate and the projected growth rate 20% will will the company need external borrowings in 2020?
3) What is the sustainable growth rate?
4) If the company grows at the sustainable growth rate how does the debt to equity ratio change?
5) Based on the 2020 growth assumptions, how much external financing will be needed?