To solve this problem, Qian uses the fact that some regions are more suitable to tea production than others: in particular, a certain amount of rain, elevation and slopes are needed to produce tea. She decides to propose an instrumental variables strategy. What is the first stage equation? An OLS regression of TEA on rain, elevation, and slope. An OLS regression of the fraction of boys on rain, elevation, and slope. An OLS regression of TEA on rain, elevation, and slope with fixed effects. O An OLS regression of the fraction of boys on rain, elevation, and slope including region fixed effects and a dummy for whether or not the country grows Orchards