That would a set of 5 numbers in ascending order with 4 being the middle one and the other 4 being the highest possible So it is
2, 3, 4, 9, 10
Mean is 28/5 = 5.6 answer
( I am assuming that each number is different)
Of duplicates is allowed then its 4 4 4 10 10 whose mean is 6.4