Suppose A1,A2,...,A20 are the vertices of a 20-sided regular polygon. Triangle with vertices among the vertices of the polygon are formed. Let m be the number of non-isosceles (scalene) trianles that can be formed one of whose sides is a side of the polygon and n be the number of non-isosceles triangles that can be formed none of whose side of the polygon. Then A)n=2m B) m+n 960 C) m+n =500 D) n-m+320