Activity a Has the Following Marginal (MB) and Marginal Cost

Short Answer

Activity A has the following marginal (MB) and marginal cost (MC) functions:
MB = 2,500 - 20A
MC = 500 + 30A
where MB and MC are measured in dollars.
-The 50^th unit of the activity increases total benefit by $_________ and increases total cost by $_________. Since marginal benefit is _________ (greater, less) than marginal cost, subtracting the 50^th unit of activity _________ (increases, decreases) net benefit by $_________.