To answer this you need to make simple thought experiment. Since the number of sales after time passes cannot go negative (note that rate at which copies are sold can drop over time but total number cannot) that means that you are adding number of sales at first hour and during first hour.
first option cannot be the answer because you are subtracting 100 copies to total number of sold copies which is not logical.
The answer is D) s(x) = 100 + 12(x-1) after 1 hour (if you replace x with 1 in equation above) you will get 100 copies which matches conditions in the text.
Since it is given that the cone and the hemisphere have the same height, and since the height of a hemisphere would be equal to its radius, the cones height must also be equal to its base radius.
With this information we can use the respective volume formulas.
Hemisphere: πr^3
Cone: πhr^2
Since h (height) = r we can say the cone volume equals:
πr^3
Now to find the ratio we divide the cone volume equation by the hemisphere volume equation
pi and r^3 cancels out from the division and we are left with