I have difficulty to do the following question,

(a)Determine (up to isomorphism) all abelian groups of order 120.

My answer:

$\displaystyle C_2 \times C_2 \times C_2 \times C_3 \times C_5$

$\displaystyle C_2 \times C_4 \times C_3 \times C_5$

$\displaystyle C_8 \times C_3 \times C_5$

(b)Verify that $\displaystyle Z_{20} \times Z_{24}/<(5,6)>$ is an abelian group of order 120. To which of the groups listed in part (a) is isomorphic?

Part (a) should be correct but I don't know how to do (b). Please help me, thank you.