$98.4^{\large\circ}F$ can be converted to $^{\large\circ}C$ as
$\large\frac{F-32}{9} = \large\frac{C}{5}$
$\large\frac{98.4 - 32}{9} = \large\frac{C}{5}$
$C = 36.88^{\large\circ}C$ or 309.88K
Then using,
$PV = \large\frac{w}{m}RT$
$\Rightarrow\large\frac{168}{760}\times6 = \large\frac{w}{32}\times0.0821\times309.88$
$\Rightarrow$ w = 1.67g
Hence answer is (c)