Part I: Run time Analysis Calculation

For each of the following code fragments calculate its runtime analysis and the $O(n)$

public void $m4($int $n$

${\displaystyle \underset{?}{\overset{?}{}}}=0$;

for $($int $)=0$;$k$

sum$++$;

$\{)=0$;$j$

sum$++$;

$\{$