Calculate the exact value of cos(20∘)cos(40∘)cos(80∘)\cos(20^\circ)\cos(40^\circ)\cos(80^\circ)cos(20∘)cos(40∘)cos(80∘).
38\frac{\sqrt{3}}{8}83
14\frac{1}{4}41
12\frac{1}{2}21
18\frac{1}{8}81