80 gm of impure sugar when dissolved in a litre of water gives an optical rotation of 9.9° when placed in a tube of length 20 cm. If concentration of sugar solution is 75 gm/litre then specific rotation of sugar is

44° 55° 66° 73°

66°

$c=\frac{θ}{IS}$ or $S=\frac{θ}{ic}=\frac{9.9}{2×0.075}⇒S=66°$