A → B The above reaction is of zero order. Half life of this...

The integrated rate equation of zero order reaction is

$kt = {A}_{0} - {A}_{t}$

Assume reaction starts with $1$ mole A

${t}_{1/2} = \dfrac{a}{2k}, K = \dfrac{1}{2 \times 50}$

For $75$ completion

${A}_{0} = a, {A}_{t} = \dfrac{a}{4}$

$a - \dfrac{a}{4} = kt$

$t = \dfrac{3}{4}\dfrac{a}{k} = \dfrac{3}{4} \times \dfrac{100}{a} = 75min$