What is the relationship between Willis Group and insurance broker in the context of the input sentence. Choose an answer from: 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.

Last week insurance broker Willis Group signed an $18 billion agreement with Towers Watson & Co to combine the companies in an all-stock deal with an implied equity value of about $18 billion.

Answer: industry