13.A thin rod whose length L is 10cm and whose mass m is 100g, suspended at its midpoint from a long wire.Its period Taof angular SHM (Simple Harmonic Motion) is measured to be 2.50 s. An irregularly shapedobject is then hung from the same wire and its period Tb is found to be 5.0s. What is the rotational inertia ofthe irregular object about its suspension axis? (The rotational inertia for a rod is   mL2  )
(A)
(B)
(C)
(D)
(E)