The regulator further said that only Bharti Airtel in Mumbai and Tata Teleservices in Delhi met the laid-down quality of service (QoS) benchmarks for call drop rate, which as per norms should be less than 2%.
What is the relationship between 'Tata Teleservices' and 'Mumbai' in the context of the input sentence.
Options: business division, headquarters location, owner of, developer