Refer to the input text as context and select the correct relationship between 'Safaricom' and 'Nairobi' from the available options.
Options: location of formation, founded by, headquarters location, developer

With over 12 million subscribers accessing the internet through its network, Safaricom pioneered its LTE Advanced (4G) proposition in December 2014, launching the most advanced version of the 4G system for mobile networks in Nairobi and Mombasa.
headquarters location