$3-$ Rainfall data for $10$ years is available. The employer wants to know about the exact amount of $10$years and $2-$years rainfall $($the amount of rainfall that on average will happen every $10$ and $2$ years$).(20p)$

$\backslash$table$[[$Year$,$Depth$($in$),,,,],[1985,14\mathrm{.}6,,,,],[1986,21\mathrm{.}7,,,,],[1987,12\mathrm{.}1,,,,],[1988,22\mathrm{.}4,,,,],[1989,23\mathrm{.}4,,,,],[1990,13\mathrm{.}1,,,,],[1991,19\mathrm{.}2,,,,],[1992,32\mathrm{.}8,,,,],[1993,11\mathrm{.}2,,,,],[1994,18\mathrm{.}2,,,,]]$