Question 1053912
Height would be x.
The other two dimensions are  (10-2x) and (50-2x).


{{{v(x)=x(10-2x)(50-2x)}}}
{{{v(x)=4x(5-x)(25-x)}}}
{{{v(x)=4x(125-30x+x^2)}}}
{{{v(x)=500x-120x^2+4x^3}}}


Instead of continuing steps to solve, what you would do next is dv/dx, equate dv/dx=0, and find x.  Figure if this is a or are max or min.