Answer
Its crushing load is 64 tons.
Work Step by Step
Insert the given data into the equation (the units don't need to be converted since the formula works with those specific units):
$4=\sqrt[4]{\frac{L\cdot10^2}{25}}$
Now, solve for L:
$4^4=(\sqrt[4]{\frac{L\cdot100}{25}})^4$
$256={\frac{L\cdot100}{25}}$
$256\cdot 25={\frac{L\cdot100}{25}}\cdot25$
$6400=L\cdot100$
$\frac{6400}{100}=L=64$