In August 2006 the Center on Addiction and Substance Abuse (CASA) at Columbia University reported results of a survey of 1297 teenagers about their views on the use of illegal substances. Twenty percent of the teens surveyed reported going to clubs for music or dancing at least once a month. Of them, 26% said drugs were usually available at these club events. Which of these percentages estimates a conditional probability? For each that does, identify the event conditioned on and the event to which the probability refers.