Reports earlier this year said Lyft's valuation was $2.5 billion based on the latest funding, which is still well below that of ride-sharing giant Uber, valued at $50 billion and backed by Chinese search engine giant Baidu (Xetra: A0F5DE - news ) , among others.
Analyze the relationship between 'Baidu' and 'search engine' within the context of the input sentence.
Options: product/material produced, employer, chairperson, currency