Jonah is playing a video racing game called checkpoint. the speed of jonah's car is recorded four times during one lap. at the first checkpoint, his speed is 80 miles per hour. at the second checkpoint, his speed has reduced by 5%. at the third checkpoint, jonah's speed has increased by the speed from the previous checkpoint. at the fourth checkpoint, his speed decreased by 20% compared with the third checkpoint. what is jonah's net change in speed between the first and fourth checkpoints?