The numerical value of $\tan 20^{\circ}\tan 80^{\circ}\cot 50^{\circ}$ is equal to

Question

$(a)\;\sqrt 3\qquad(b)\;\large\frac{1}{\sqrt 3}$$\qquad(c)\;2\sqrt 3\qquad(d)\;\large\frac{1}{2\sqrt 3}$