The moment of inertia of a system of four rods, each of length 'l' and mass 'm', about the axis shown is
Moment of inertia about 'z'.
I2=4(ml23sin2 45∘)
I2=2ml23
Applying parallel axis theorem,
I1=I2+4m(I√2)2
=2ml23+4ml22
I1=83ml2