Determine the molecular formula of an oxide of iron, in which the mass percent of iron and oxygen are $69.9$ and $30.1$, respectively.

$$\begin{gathered} \mathrm{A} : 36.4527 \mathrm{u} \\ \mathrm{B} : 35.4527 \mathrm{u} \\ \mathrm{C} : 34.4527 \mathrm{u} \end{gathered}$$

Enter your correct answer as $\mathrm{A}, \mathrm{B} \mathrm{or} \mathrm{C}$

Number of moles of carbon atoms.
(Only mention the number, not the unit)

In three moles of ethane $\left({\mathrm{C}}_2{\mathrm{H}}_6\right)$, calculate the following:

The number of moles of hydrogen atoms. 

In three moles of ethane $\left({\mathrm{C}}_2{\mathrm{H}}_6\right)$, calculate the following:

The number of molecules of ethane. 

(Provide correct answer upto two decimal places and no need to mention units).