Answer:
10,500
Explanation:
See this as 2 rectangles: a box of water (28cm), and another box with the height you want (35cm)
Area of Rectangle = lwh
For the water;
50 x 30 x 28= 42000
As for the needed volume:
50 x 30 x 35 = 52500
To find how much more water, subtract the smaller volume from bigger volume.
10500 should be the final answer