Explanation

(a) Let initial kinetic energy, $E_{1} = E$
Final kinetic energy, $E_{2} = E + 300\%$ of $E = 4E$
As $P \propto \sqrt{E} \Rightarrow \frac{P_{2}}{P_{1}} = \sqrt{\frac{E_{2}}{E_{1}}} = \sqrt{\frac{4E}{E}} = 2 \Rightarrow P_{2} = 2P_{1}$
$\Rightarrow P_{2} = P_{1} + 100\%$ of $P_{1}$
$i.e$., Momentum will increase by 100%