What is the relationship between cornerstone and marketing 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.

And while 150,000 views is an incredibly impressive number, what is even more exciting is how the webcast has become a cornerstone for an entirely new digital marketing strategy for Walker & Dunlop.

Answer: industry