4. (Calculate an ROI) A lifestyle publication is trying to gain web subscriptions, which cost $10 a month. They create a post about the trial for Twitter which includes a tracking URL that leads to the free-trial landing page. They boost the post for four days with a budget of $25 per day. In the time span of the posted boost, they'd received 100 visitors and 20 signed up for a free trial. Of the 20, four become paid subscribers. What is ROI for the paid social media promotion? Based on the results, what is your suggestion