The 1st boy says, "My Dad's the fastest man in the world."
"How do you know that?" Ask the other boys.
"Because he can fire a bow and arrow and run and catch it!" He replies.
"That's nothing," says the 2nd boy. "My Dad can fire a gun and run and catch the bullet!"
"That's nothing," says the 3rd boy, "My Dad works for the Council, he finishes at half 4
Spoiler:
