A study was done to determine the efficacy of three different drugs: A, B, and C in relieving headache pain. Over the period cov
ered by the study, 50 subjects were given the chance to use all three drugs. The following results were obtained: 21 reported relief from drug A.
21 reported relief from drug B.
31 reported relief from drug C.
9 reported relief from both drugs A and B.
14 reported relief from both drugs A and C.
15 reported relief from both drugs B and C.
41 reported relief from at least one of the drugs.
Note that some of the 21 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?
b) How many people got relief from all three drugs?
