Suppose additional investment in health (going from 19 units to 20 units of health stock) costs $800 but will only yield benefits of $200. Based on the Grossman's pure investment model, which of the following can potentially be the optimal units of health stock? Suppose additional investment in health (going from 19 units to 20 units of health stock) costs $800 but will only yield benefits of $200. Based on the Grossman's pure investment model, which of the following can potentially be the optimal units of health stock