In order to solve this, you're going to need something called "absolute value" (it's basically putting vertical lines around a term like |x| ). And you're going to use it for all the values you have, and find the largest number. This is simply because absolute value literally means the distance from zero. So, doing the problem for you: you'd start off by finding the absolute value for each of those values [3/8 ,0.27, 0.3, 4/7]. It is only a matter of finding out that 4/7 is the largest of those four numbers. Hope I helped :)
Since we know that the volume of a sphere is 4/3 the volume of a cylinder, we can multiply 21*4/3. 21*4 will equal 84 and 84/3 would be 28. So the volume of the sphere would be 28 meters cubed.
