Answer:
a) 
b) 
c) 
Explanation:
Hello,
a) In this case, the given height in cm is:

And the radius in cm is:

Thus, the volume in cubic centimeters which is also equal in mL (1cm³=mL) is:

b) In this case, the given height in mm is:

And the radius in mm is:

Thus, the volume in cubic millimeters is:

c) Finally, since 1000 mL equal 1 L, the required density in g/L turns out:

Best regards.
1kg is about 2.2 pounds. So 4kg = 8.8 pounds. If that represent 19% of the total, here is the answer.
0.19*x=8.8
x=8.8/0.19
x=46.31 pounds
8 protons in oxygen bc it has an atomic number of 8