The first week is 10 x 1.4.
The second week is that answer x 1.4 etc.
So you are only multiplying the first week by 10.
{ [ 10 x 1.4) x 1.4] x 1.4}. Since multiplication is commutative, we don’t need the grouping symbols...
10 x 1.4 x 1.4 x 1.4
That s answer A