________________________ Paid 10 dollars for every 20 party-subs made. ________________________ Studying for a class that has pop quizzes. ________________________ Slots machines are based on this schedule. ________________________ Feeding a puppy every time it sits when you command. ________________________ Speed traps on the highway. ________________________ Selling cookies door-to-door. ________________________ Getting the clothes out of the dryer after you hear the buzzer. ________________________ Going up a staircase to reach a landing with a nice view. ________________________ Doing 20 pushups to help stay fit. ________________________ Playing Bingo. ________________________ Getting a paycheck at the end of 2 weeks.