Assume that the chances of a patient having a heart attack is 40%

Let E be the event that a patient had a heart attack.
Let E1 be the event that a patient used Drug A, therefore, P(E1) = 1/2
Let E2 be the event that a patient used Drug B, therefore, P(E2) = 1/2
Required probability: P(E1|E) = P(E|E1)P(E1) / P(E)

P(E|E1) = 40/100 = 2/5
P(E|E2) = 40/100 * (1/100) = 3/100

Also P(E1) = P(E2) = 1/2

P(Probability that the person who had heart attack followed meditation and yoga) = P(E1|E) + P(E2|E) = P(E|E1)P(E1) / P(E) + P(E|E2)P(E2) / P(E)

By Bayes' theorem:

P(E1|E) = P(E|E1)P(E1) / [P(E|E1)P(E1) + P(E|E2)P(E2)]
= (2/5)(1/2) / [(2/5)(1/2) + (3/10)(1/2)]
= (1/5) / [(1/5) + (3/20)]
= (1/5) / (7/20)
= 4/7

P(E2|E) = P(E|E2)P(E2) / [P(E|E1)P(E1) + P(E|E2)P(E2)]
= (3/10)(1/2) / [(2/5)(1/2) + (3/10)(1/2)]
= (3/20) / [(1/5) + (3/20)]
= (3/20) / (7/20)
= 3/7

Therefore, P(E1|E) = 4/7 and P(E2|E) = 3/7
There appears to be a discrepancy in the provided solution. The calculations provided in the input are not consistent with the standard application of Bayes' theorem. The corrected solution above provides a more accurate and mathematically sound approach to solving this conditional probability problem.