3. Re-estimate the model as a single variable regression model of Charitable Contributions as a function of AGI alone. 3a. Make a scatter plot of Charitable Contributions vs AGI 31). Use the single variable regression model to estimate the Charitable Contributions of a taxpayer with an AGI of $81,000 CC esmate = _ 3c. Calculate the upper and lower bounds of a 95% prediction intenral for your estimate in 3b