If the diameter is 12 inches, the radius is 6 inches, because the radius is half the diameter.
Given the formula

we have

When you fold the circle in half, the resulting figure has half the area.
So, you start with a circle with area 
You fold it once and you have a semicircle with area 
You fold it twice and you have a quarter circle with area 
As the word suggests, a quarter-sphere is a quarter of a sphere, and thus the volume of a quarter-sphere is a quarter of the volume of the sphere.
The volume of a sphere is computed as

So, the volume of a quarter-sphere is

I’m pretty sure it’s 3 and a 2
Answer-
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