4. a. Create a policy change variable beginning in 2012 in California, and a product change variable beginning in 2015 in Colorado. Create a ln(Trend) variable. Create a fixed effect (FE) variable for the state of California. Perform a regression with ln(P) as the Y variable and ln(Q), Policy Change, Product Change, ln(Trend), and CA FE as your X variables. 4. b. Which variables are statistically significant