Answer
$T=76.3$ ns
Work Step by Step
As we know that time period and frequency are reciprocal of each other so
$T=\frac{1}{f}$
$T=\frac{1}{13.1\times 10^6}$
$T=7.63\times 10^{-8}$
$T=76.3\times 10^{-1}\times 10^{-8}$
$T=76.3\times 10^{-9}$
$T=76.3$ ns
