Question 21
We place 100 table tennis balls inside $n$ boxes so that the number of balls in each box contains the digit 8, such as 8 balls, 18 balls, 83 balls and 88 balls. When $n=3$, the number of table tennis balls in the boxes are 8, 8 and 84 respectively. If $n=5$, and two of the boxes have the same number of balls while other boxes have different number of balls, what is the largest total number of balls in two boxes?