A tiger is 40 ft directly south of a herd of elephants. The tiger starts to slink towards the elephants at a rate of 3ft/sec, 4 seconds after the tiger starts his path towards the elephants, one elephant bolts directly east at a rate of 7 ft/sec. How fast is the distance between the tiger and the bolting elephant changing 4 seconds after the elephant leaves the herd, assuming the tiger continues on his path towards the herd?