Answer
Store B, 450,000
Work Step by Step
I would like to own store B since its sales have been constantly increasing for every year since 2014. Assuming that there is the same amount of growth between 2018 and 2017 as there is between 2017 and 2016, the amount of sales I would predict is:
$$ = 400,000 +50,000 \\ = 450,000$$
