To test the effect of billboard advertising on sales revenue, you decide to run an experiment. In Market X, you advertise using billboards for a month, in another distinct market that is very similar, Market Y, you do not. Suppose nothing else changes in either market over this period and that there are no spillovers (i.e. nobody is seeing the billboards and then shopping in Market Y). If you found that sales revenue went up by $100,000 in Market X during the month and that sales revenue went down by $20,000 in Market Y, what is the difference in difference estimate of the billboard advertising on sales revenue?

1)Increase of $100,000 in sales revenue.

2)Increase of $80,000 in sales revenue.

3)Decrease of $20,000 in sales revenue.

4)Increase of $120,000 in sales revenue.

5)Decrease of $80,000 in sales revenue.