The horizontal distance of a kite from the boy flying it is 30 m and 50 m of cord is out from the roll. If the wind moves the kite horizontally at the rate of 5 km per hour directly away from the boy, how fast is the cord being released ?

• A. 3 km per hour
• B. 4 km per hour
• C. 5 km per hour
• D. 6 km per hour