I am not sure whether it is the one I have or the last one.
You are so close.
As n increases, a_n should also increase, however in the choice you selected, a_n decreases.
a_1 = 1200, a_2 = 420.
When it says increase by, you add a 1 to it. 1 + .35 = 1.35.
If the starting value is x, and you want to increase it by 35%, you are looking for x + .35x = (1+.35)x.