In △ABC\triangle ABC△ABC, a=8,b=7,c=5a=8, b=7, c=5a=8,b=7,c=5. Find cos(B)\cos(B)cos(B).
12\frac{1}{2}21
14\frac{1}{4}41
17\frac{1}{7}71
18\frac{1}{8}81