Consider the grouped frequency distribution below.

$\backslash$table$[[\backslash$table$[[$Classes$],[($Time$)],[($minutes$)]],\backslash$table$[[$Frequency$,],[$f$]],\backslash$table$[[$Cumulative$],[$Frequency$]],\backslash$table$[[$Midpoint$,],[$m$]],$fm$,$fm$^(2)],[\backslash$tabletableB$,21\mathrm{.}00,168,3528],[\backslash$tableA$,29,25\mathrm{.}00,450,11250],[\backslash$tableSigma $,35,,,,]]$

The missing value $B$ is: