Mark and kathy take their 2-year-old son to the supermarket every saturday. each week, the same sequence of events unfolds: their son screams, demanding that they buy him treats. although they refuse to give in to his demands, he continues to scream. finally, either mark or kathy gets in their son's face and yells at the top of their lungs "shut up! " he stops screaming instantly. what operant conditioning concepts are illustrated in this story?