Answer
$I_{O}=1.36$ kg*m$^2$
Work Step by Step
$I_{O}=\Sigma I+md^2=[\frac{1}{12}(1.2)^2(3)(1.2)+3(1.2)(0.2)^2]+[(\frac{1}{12}(0.4)(3)(0.4)^2+(0.4)(3)(0.4)^2]=1.36$ kg*m$^2$
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