Given the input sentence, please extract the subject and object containing a certain relation in the sentence according to the following relation types, in the format of "relation1: word1, word2; relation2: word3, word4". Relations include: 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.
Text: The week's deals included the $28.3 billion purchase of insurer Chubb by Swiss insurer Ace Limited (NYSE: ACE - news ) ; the $6.8 billion acquisition of Health Net (NYSE: HNT - news ) by rival health insurer Centene; and the decision by US professional services company Towers Watson and insurance broker Willis Group to combine in a deal with an implied equity value of about $18 billion.
user
industry: Willis Group, insurance broker
assistant