Answer
Jan. 2011$:\quad [236\quad 127 \quad 136\quad 191]$
Feb. 2011$:\quad [230\quad 122 \quad 135\quad 190]$
Work Step by Step
The table suggests three matrices:
$A=[238\quad 140 \quad 149\quad 205]$
$B=[-2\quad -13 \quad -13\quad -14]$
$C=[-6\quad -5 \quad -1\quad -1]$
The median price in Jan. 2011 is obtained by
$A+B=[238-2\quad 140-13 \quad 149-13\quad 205-14]$
$=[236\quad 127 \quad 136\quad 191]$
The median price in Feb. 2011 is obtained by
$A+B-C=[236-6\quad 127-5 \quad 136-1\quad 191-1]$
$=[230\quad 122 \quad 135\quad 190]$
