Answer
$M = 2.5~kg$
Work Step by Step
We can use the parallel axis theorem to find the mass:
$I = I_{com}+Mh^2$
$Mh^2 = I - I_{com}$
$M = \frac{I - I_{com}}{h^2}$
$M = \frac{I_B - I_A}{h^2}$
$M = \frac{0.150~kg~m^2 -0.050~kg~m^2}{(0.2~m)^2}$
$M = 2.5~kg$
