Answer
(a) $I = \frac{mL^2}{2}$
(b) $I = \frac{11mL^2}{16}$
Work Step by Step
(a) $I = 2\times mr^2$
$I = 2\times m~(\frac{L}{2})^2$
$I = \frac{mL^2}{2}$
(b) $I = m_1~r_1^2+m_2~r_2^2+m_3~r_3^2$
$I = m~(\frac{L}{4})^2+m~(\frac{L}{4})^2+m~(\frac{3L}{4})^2$
$I = \frac{11mL^2}{16}$
