Assume the middle implies that the median and mean=4. The minimum size of such a set is 3, where 4 is the central value. The sum of the three values must be 12 so that the mean is 4. If x is the low value then x+4+8=12, and x must be 0. If the mode of the set is also 4 then we have a set of 5: 0, 4, 4, 4, 8 and median=mode=mean=4. In each case 0 is the low value.