ACCA F9 , September 2016 Question 32 , selling price with inflation calculation

Selling price in year 1 is 15, year 2 is 18 , year 3 is 22 and year 4 is also 22.

Inflation is 4% per year.

So, selling price for year 1 is = 15*1.04 = 15.6
But selling price for year 2 is 19.47

kindly help me how this 19.47 is calculated

ok it seems finally my brain clicked , it should be 18*1.04^2
I was calculating 18*1.08