Given phrases that describe the relationship between two words/phrases as options, extract the word/phrase pair and the corresponding lexical relationship between them from the input text. The output format should be "relation1: word1, word2; relation2: word3, word4". Options: 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.

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.

Answer: headquarters_location: Safaricom, Nairobi