QUESTION $($#$10)$ CARRIES MAX. $15$ POINTS

A large river basin$/$watershed is divided into nine sub$-$basins with drainage areas of:

$($a$)25,300k{m}^2,($b$)50,100k{m}^2,($c$)35,200k{m}^2,($d$)5,200k{m}^2,($e$)18,600k{m}^2,$

$($f$)32,400k{m}^2,($g$)20,800k{m}^2,($h$)37,200k{m}^2,$ and $($i$)10,800k{m}^2.$

The average annual precipitation for each of the above listed sub$-$basin is respectively:

$($a$)98cm,($b$)75cm,($c$)68cm,($d$)49cm,($e$)52cm,($f$)35cm,($g$)91cm,($h$)53cm$ and

$($i$)50cm.$

What is the average annual precipitation for the overall river basin?

a$)$ Using the Thiessen Polygon or Weighted Average Method

b$)$ Using the arithmetic average method