Given a $2$ dimensional array dimensions $n$ by $m$ of distinct positive integers, you wish to find the largest

difference $A-B$ where $A$ is in a column to the left of $B.$

For the above example, your algorithm should return $16$ which is the maximum difference coming from

$19-3=16.$

$($Your algorithm must be a divide and conquer algorithm. No justification necessary. Compute your

runtime analysis using Master's theorem.$)$