Which of the following markets is an example of monopolistic competition?​

Captain john's yachts, inc., located in fort lauderdale, florida, rents three types of ocean-going boats: sailboats, cabin cruisers, and captain john's favorite, the luxury yachts. captain john advertises his boats with his famous "you rent"we pilot" slogan, which means that the company supplies the captain and crew for each rented boat. each rented boat has one captain, of course, but the crew sizes (deck hands, galley hands, etc.) differ. the crew requirements, in addition to a captain, are one for sailboats, two for cabin cruisers, and three for yachts. ten employees are captains, and an additional 18 employees fill the various crew positions. currently, captain john has rental requests for all his boats: four sailboats, eight cabin cruisers, and three luxury yachts. if captain john's daily profit contribution is $50 for sailboats, $70 for cruisers, and $100 for luxury yachts, how many boats of each type should he rent?

Russell's study compared gpa of those students who volunteered for academic study skills training and those who did not elect to take the training. he found that those who had the training also had higher gpa. with which validity threat should russell be most concerned?

Janis owns and operates a store in a country experiencing a high rate of inflation. in order to prevent the value of money in her cash register from falling too quickly, janis sends an employee to the bank four times per day to make deposits in a interest-bearing account that protects the store's revenues from the effects of inflation. this is an example of the (menu costs/ unit of account costs/ shoesleather costs) of inflation. pick one