Utilize the input text as a context reference, choose the right relationship between Lehman Brothers and investment bank 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.

Lehman Brothers LEH.N shares fell sharply on Monday on speculation that the investment bank could be bought for $15 a share, a price well below current market levels.

Answer: product_or_material_produced