Solution: D. 25 KM
Analysis:
We can find BC with the law of cosine. We know two sides and the included angle.
[tex]\begin{gathered} BC^2=AB^2+AC^2-2AB\ast AC\ast cosA \\ BC=\sqrt{(14)^2+(21)^2-2\ast14\ast21\ast cos(89)} \\ BC=\sqrt{196+441-10.26} \\ BC=\sqrt{626.74}=25.03\text{ } \end{gathered}[/tex]
