Cocaine users commonly snort the powder up the nose through a rolled‑up paper currency bill. spain has a high rate of cocaine use, so it's not suprising that euro paper currency in spain often shows traces of cocaine. researchers collected 20 euro bills in each of several spanish cities. the plus four method is particularly useful when there are no successes or no failures in the data. the study found that in seville, all 20 of a sample of 20 euro bills had cocaine traces. (a) what is the sample proportion p^ of contaminated bills? (enter your answer rounded to a whole number.)