Calculate molecular diameter of He from its Vander Waal's constant b = 24mL$mol^{-1}$

Question

$(a)\;271 \overset{\circ}{A}\qquad(b)\;282 \overset{\circ}{A}\qquad(c)\;2.71 \overset{\circ}{A}\qquad(d)\;0.27 \overset{\circ}{A}$