Im no genius or sure if its right, but I would definetly go with (12,4)
What they said at the top
I think it's 81, but not quite sure.
Each costume needs 58 yards of ribbon and since you have 24 costumes, you need to multiply both of them.
58×24=1392
Assuming
![f(x,y,z)=\dfrac{10}{x^2+y^2+z^2}](https://tex.z-dn.net/?f=f%28x%2Cy%2Cz%29%3D%5Cdfrac%7B10%7D%7Bx%5E2%2By%5E2%2Bz%5E2%7D)
, and not
![10x^2+y^2+z^2](https://tex.z-dn.net/?f=10x%5E2%2By%5E2%2Bz%5E2)
(which is easier to work with, but not by much).