A study was done to determine the efficacy of three different drugs—A, B, and C—in relieving headache pain. Over the period covered by the study, 50 subjects were given the chance to use all three drugs. The following results were obtained. "22 reported relief from drug A 22 reported relief from drug B 31 reported relief from drug C 7 reported relief from both drugs A and B 15 reported relief from both drugs A and C 16 reported relief from both drugs B and C 43 reported relief from at least one of the drugs" Note that some of the 22 subjects who reported relief from drug A may also have reported relief from drugs B or C. A similar occurrence may be true for the other data. (a) How many people got relief from none of the drugs?