Background: Robert Mondavi has great pride in his wine. In fact, he is a legend up North for his technical improvements and marketing strategies brought worldwide recognition for the wines of the Napa Valley in California. He recently dabbled in advertising his product on Facebook. While he wants to try the "social thing"-you suggest that "the relationship between advertising display ads on Facebook and sales is positive & somewhat linear- but the story isn't that simple... Below is the data. Problem: Ad. Expense $2,500 $3,000 $3,500 4,000 $4,500 5,000 $5,500 6,000 $6,500 7,000 7,500 $8,000 $8,500 9,000 9,500 $10,000 Sales 95,000 110,000 124,000 $138,000 $143,000 $147,000 149,000 155,000 169,000 $185,000 187,000 192,000 195,000 $198,000 $203,000 $225,000 Why is the story not so simple? What is going on here? (Make sure you research "display ads" on Facebook prior to answering)