Answer
175 mL
Work Step by Step
Millilitres of halothane= $1.00\times10^{24}\,Br\,atoms\times\frac{79.904\,g\,Br}{6.02214\times10^{23}\,Br\,atoms}\times\frac{197.4\,g\,C_{2}HBrClF_{3}}{79.904\,g\,Br}\times\frac{1\,mL\,C_{2}HBrClF_{3}}{1.871\,g\,C_{2}HBrClF_{3}}$
$=175\,mL\,C_{2}HBrClF_{3}$