Firm X wants to evaluate how effective its paid search campaign is. To do so, the firm divided its customer base into two groups and exposed the paid ad once to 100,000 customers out of 110,000 customers in total. Then the firm obtained the following conversion data: Based on the data above, what would be the incremental conversion rate due to the campaign (i.e., the true treatment effect)? 2% 5% 7% 12%