3. (30} Your best friend from high school has invented a delicious taco called "The Robust.\" They sell it out of 40 food trucks at different locations in California. Your friend would like your help estimating a demand curve for their taco. 3A. Your friend gives you the data from a day of taco sales at each of the 40 food trucks, and asks you to estimate a demand curve. They let each taco truck driver set their own price, so there's lots of variance in prices. OJ=BD+BIPi+Ui ,l=1t040. You look at the data and discover that the correlation of Q and P is positive in this sample. Your friend laughs at you, --they learned in high school that demand curves slope downwards. Explain how a positive correlation of Q and P might happen, by describing at least one real life omitted variable that might result in a positive correlation, and using the terms linear causal effect and the omitted variable bias formula