A 15-foot plank leans against a vertical pole. The top of the plank begins to slide down the pole at a steady speed of 2 inches per second. How fast is the bottom of the plank moving away from the pole when it is 8 feet away from the base of the pole (in inches per second)?

• A. $dx/dt=1.58\frac{in}{s}$
• B. $dx/dt=3.46\frac{in}{s}$
• C. $dx/dt=5.04\frac{in}{s}$
• D. $dx/dt=3.17\frac{in}{s}$