There are twenty numbered balls in a bag. Two of the balls are numbered 0, six are numbered 1, five are numbered 2 and seven are numbered 3, as shown in the table below. Number on ball (0, 1, 2, 3), Frequency (2, 6, 5, 7). Four of these balls are chosen at random, without replacement. Calculate the number of ways this can be done so that

1. (a)A lock can be opened using only the number 4351. State whether this is a permutation or a combination of digits, giving a reason for your answer.[1]
2. (b)(i)the four balls all have the same number,[2]
3. (b)(ii)the four balls all have different numbers,[2]
4. (b)(iii)the four balls have numbers that total 3.[3]