DK-GEORGMOHR 2025 Problem 2

In the boxes in the top row of the figure, the numbers $4, a, b, c, 4, 9$ are written as shown in the figure, where $a, b$ and $c$ are among the numbers $0, 1, 2, ... , 9$ . In each box lying below two other boxes, one writes the last digit of the sum of the two numbers in the boxes above. Which numbers may be written in the bottommost box?