(1) all different
5,0,1,9⇒⌊3=6 ways
(2) 2 alike, 2 different
5,0,0,1⇒3 ways
5,1,1,2⇒3 ways
5,2,2,0⇒3 ways
5,2,2,9⇒3 ways
5,5,0,2⇒6 ways
5,5,2,9⇒6 ways
5,1,9,9⇒3 ways
(3) 3 alike, 1 different
5,5,5,0⇒3 ways
5,5,5,9⇒3 ways
(4) 2 alike, 2 other alike
5,5,1,1⇒3 ways
Total ways =42