Answer
Some possible reasons why Store B's sales has overtaken Store A's sales:
Store B started to provide better customer service than Store A.
Store B started to offer a better rewards or loyalty program than Store A.
There are a number of possible reasons other than the ones mentioned above.
Work Step by Step
(answers vary)
There are a number possible reasons why Store B's sales exceeded the sales of Store A.
Some possible reasons are:
Store B started to provide better customer service than Store A.
Store B started to offer a better rewards or loyalty program than Store A.