How many hydrogen atoms does it take to make up the mass of the earth$(6\times {10}^{24 }\mathrm{kg})$? ( in number of hydrogen atom)

How many molecules are there in a human body( of mass 60 kg)?

Assuming that the mass of a person is made up entirely of water $(molar mass of water = 18 g/mol)$. 

What is the density of a proton in an order of magnitude estimation? (in $kg/m^3$)

Mass and radius of the proton ${10}^{-27} kg$ and ${10}^{-15} m$ respectively.

For the diameter of the solar system$({10}^{13} m)$, how long does light take to transverse? (in ${10}^4$sec)

$c = 3\times {10}^8 m/s$.