Utilize the input text as a context reference, choose the right relationship between Dick Costolo and Twitter from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

Former Twitter boss Dick Costolo was replaced this month on an interim basis by co-founder Dorsey, who also runs Square Inc., a mobile-payments company.

Answer: employer