i have one question :

123 Inc has a profit margin of 15%. Its total asset turnover ratio is 2 and its dividend payout ratio is 60%. What is the company's internal growth rate?

from the slide, the formula should be:

ROA*retention ratio= 15%*2*(1-60%)=12%

but the answer is 12%/(1-12%)=13.64%, i don't know why?

why i should divide 12%by(1-12%)??,the internal growth rate should be ROA*retention ratio.