CFA AM 2011 - Question 4A - Just Cobb Douglas?

Part A asks for annual real GDP growth for 4 points, just looks like plug and chug for the answer of 5.56% but what do you need to do to get the 4 points?

I just wrote out the formula with the numbers and the answer but are you expected to write the actual formula or do you need to write some background about how the formula estimates the growth rate?