51. Radius OA of the circle shown below is perpendicular to AP. The circle intersects OP at B. The length of AP is 12 centimeters, and the measure of ∠APO is 20°. Which of the following values is closest to the length, in centimeters, of BP ？

(Note: sin 20°≈ 0.342, cos 20°≈ 0.940, and tan 20°≈ 0.364)