Utilize the input text as a context reference, choose the right relationship between Sabadell and euro 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.

MADRID, Sept 14 (Reuters) - Spanish bank Sabadell is considering making a bid for an 18 billion euro ($20.4 billion) mortgage portfolio held by British nationalised banks Northern Rock and Bradford & Bingley, a source familiar with the process said on Monday.

Answer: currency