Using prismoidal method, what is volume $($cubic metre$)$ of earthwork required for $10m$ deep pit, if the top and bottom dimensions are $4m8m$ and $8m16m$ respectively?

$($a$)678\mathrm{.}34$

$($b$)746\mathrm{.}67$

$($c$)800$

$($d$)1493\mathrm{.}33$

asper my knowledge, there is $2$ solutions to this questions. $1-$ we find the mean of the dimensions and find the mean area. $2-$ we find the mean area directly from the other $2$ areas. the answer we get in bith the cases are fiven in optionso what to do$?$