suppose that a small company is thinking of putting plants in their lobby for employees to view and enjoy. since the plants are to be viewed by employees, the plants are non-excludable (it is infeasible to move a plant each time a specific individual walks by) and non-rival in consumption (if one worker looks at the plant, it does not prevent another from doing so as well). the company employs three workers: robin, tyler, and sharon. the company is thinking about buying up to three plants, and wants to know how much workers would enjoy each plant. for robin, the first plant has a benefit of $31 per day, the second plant has a benefit of $19 per day, and the third plant has a benefit of $9 per day.