统计概率的计算,

题目

统计概率的计算,
Your store is interested in learning more about customers’ purchasing
patterns and how they relate to the frequency of store visits.The probability
that a customer’s visit will result in a purchase is 0.35.The probability that
a customer has been to the store within the past month is 0.20.Of those who
did not buy anything,12% had been there within the past month.
a.Find the probability of making a purchase given that the customer had been to the store within the past
month.
b.What percent of customers are frequent shoppers,defined as making a purchase and having been to thestore within the past month?
答案分别是：0.61 & 0.122

答案