This is just a dimensional analysis problem in disguise. Here, the conversion factor is the ratio of carbon to hydrogen in the molecular formula of testosterone. These units are defined below so that mathcad doesn't flip out:
In 1 mol of testosterone, there are 6.02 x 1023 testosterone molecules; this is our conversion factor between molecules and moles. In part (b), we found that the sample contained 2.53 x 1019 testosterone molecules. We have
Here, we use the molar mass of testosterone to convert between grams and moles: this is the mass, in grams, of 1 mol of the substance. Numerically, the molar mass is the same thing as the formula weight; we just change the units from amu to units of grams / mole. First, we get the molar mass by adding up the atomic masses:
