a b c d

b

$\xi = L\frac{\Delta I}{\Delta t}= L \frac{ 25 -10}{1} = 15L$ $ \Rightarrow L = \frac{25}{15}=\frac{5}{3}$ $\text{Change in Energy is }\Delta E = \frac{1}{2} L(I_f^2 - I_i^2) = 437.5J$