Answer:
a) Jacob will earn $600000. 5/6 of his annual salary will be economic rent.
b) The advertising company will not be able to make an economic profit because if they withhold some additional revenue made because of hiring person J, then person J will switch to another advertising company at a higher salary and that company keep on making profits. The company should bid for Person J until firms are indifferent between paying him $600,000 or hiring someone else for $100,000. Thus, the bidding of person J will continue until the salary of person J has bid up to a level where no company can make economic profits.
Explanation:
See the attached pictures for explanation.