3. A box has 20 + 1 balls, marked consecutively as -0,-(0-1),...,-1,0, 1,..., (0- 1), 0, where 02 10 is an unknown integer. (So, we know that the box contains at least 21 balls, but not the exact number.) Suppose 20 balls are selected at random and without replacement and the marks on the selected balls, denoted X,..., X20 are recorded. (a) Find a statistic that is minimal sufficient for and derive its distribution. (b) Is the minimal sufficient statistic in (a) also complete.