Solve the all parts of following problem given below:
Problem: A person riding in the back of a pickup truck traveling at 60km/h on a straight, level road throws a ball with a speed of 10km/h relative to the truck in the direction of the truck's motion.
Part I: What is the velocity of the ball relative to a stationary observer by the side of the road?
Part II: What is the velocity of the ball relative to the driver of a car moving in the same direction as the truck at a speed of 80km/h?
I need help to solve the above problem and express your answer as a whole number.