How does g(x) = 2*0.6^x change over a unit interval in x. *Options/question are in image

I found a problem that discusses tennis balls in cartons and boxes.

1 box contains 10 tennis balls.
1 carton contains 10 boxes of tennis balls for a total of 100 tennis balls.

So, if you buy 4 boxes, you'll get 40 tennis balls. 10 * 4 = 40
If you buy 4 cartons, you'll get 400 tennis balls.
4 cartons * 10 boxes/carton * 10 tennis balls/box = 400 tennis balls.