4. COVID-19 provided interesting applications of the supply and demand model. How did it possibly change the demand for certain goods such as hand sanitizer? Explain why there was a shortage of some goods. How did people change their behavior when their income changed (remember a lot of people lost their jobs). Relate the income change to inferior/normal goods and substitutes/complement (6 points). Finally, what are the incentives (good or bad) during this pandemic that may have led people to behave nicely (or poorly)?