First of all Cr=1s2 2s2 2p6 3s2 3p6 4s1 3d5

electrons in l=1 : 12

Electrons in l=2 : 5

This is because :

For l = 0 1 2 3 4 5 ..........

Notation = s p d f g h ..........

These are some very basic question from the chapter Structure of Atom. You need to practice more such questions to ensure your scoring marks in entrance exams.

Best wishes. Thankyou.