$(10$ points$)$ Write a Scheme procedure $($manhattan a b$)$ which, given two pairs representing two points on the Cartesian coordinate system, returns the Manhattan distance between the two points.$$

For example:$$

$>($manhattan $\text{'}(-1.4)\text{'}(1.8))$

$6$

$>($manhattan $\text{'}(-4.-3)\text{'}(6.3))$

$16$

Copy your Scheme code without formatting in the box below: