Answer: Choice D
m = n
b = sqrt(pi)*a
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Step-by-step explanation:
Each circle has a radius of 'a'. So r = a.
The area of each circle is pi*r^2 = pi*a^2
The area of each square with side length b is b^2
The two stacks have the same volume only when the circle area is equal to the square area, so whenever pi*a^2 = b^2 is true.
Solving for b leads to b = sqrt(pi*a^2) = sqrt(pi)*a
The stacks must also be the same height for the volumes to be the same, so m = n as well.