A hot air balloon rising upwards is noticed by an observer who is 4 miles from where it is released. At this exact moment, the angle between the observer's line of sight and the horizontal is pi/3...

A hot air balloon rising upwards is noticed by an observer who is 4 miles from where it is released. At this exact moment, the angle between the observer's line of sight and the horizontal is pi/3 radians. The angle of elevation is changing at 0.3 radians per minute. How fast is the hot air balloon rising right now?