$8\mathrm{.}12.$ Given the following average demand for each month, calculate the seasonal indices for each month.

$\backslash$table$[[$Month$,$Average Demand,Seasonal Index$],[$January$,30,],[$February$,50,],[$March$,85,],[$April$,110,],[$May$,125,],[$June$,245,],[$July$,255,],[$August$,135,],[$September$,100,],[$October$,90,],[$November$,50,],[$December$,30,],[$Total$,,]]$

Note that your answer, if done correctly, should have all the seasonal indices add up to the number of periods in the entire season, in this case $12.$