The amount of balls in a given layer can be found by squaring the layer it is in
4 layers
top layer (1st) is 1
2nd is 4
3rd layer is 9
4th is 16
add them up
1+4+9+16=30
30 in that pyramid
This is binomial probability with n=50 and p=0.62.
We want binom(50,0.62,35).
One way to calculate this is to use a calculator with statistical functions.
My TI-83 Plus turned out the result 0.061.
Volume of cube=side length cubed
1/4^3=0.015625in^3