#### Answer

a. negative influence of A on B.
b. no influence of A on B
c. positive influence of A on B

#### Work Step by Step

Clearly the event "remembers a certain product commercial"
have some effects on the event "buys the product".
a. P(B|A) = 0.20
The probability is reduced indicating a negative influence of A on B.
b. P(B|A) = 0.35
No change of probability indicates no influence of A on B
c. P(B|A) = 0.55
An increase in probability indicates a positive influence of A on B