suppose you want to perform two sums: one sum of $5$ scalar variables and a one is a matrix sum of pair of two dimentional arrays with dimensions $5$ by $5.$ if you use $10$ processors, the execution time after improvement $=$

$25\mathrm{.}6t$

$7\mathrm{.}5t$

$6\mathrm{.}25t$

$5\mathrm{.}7t$