The Conical Funnel

I have a conical funnel similar to the one used in the Chemistry laboratory, but a bit different. I put into it 5 marbles of different sizes. The marbles are such that they touch each other and the wall of the funnel, but the lower-most marble does not fall out. Find the amount of water the middle marble (3rd from top) can hold if it is hollow. Assume its inner radius to be equal to its outer radius. The radii of the uppermost and lowermost marble are 18 mm and 8 mm respectively.

Level: Easy-Medium

Scoring System

QUESTIONS given:

1. Awesome questions which involve good thinking and which are within our level will be awarded 1 point.
   
2. Medium level questions include Lateral Thinking & Table Problems and will be awarded 0.5 point.
   
3. Stupid easy questions are worthless!
   
4. Any question above our level of thinking will be awarded -0.5 point as it will simply mean time wastage by the other members.

ANSWERS given:

1. Awesome Question: 2 points
   
2. Medium level: 1 point
   
3. Easy Question: 0.5 point