In response, the company responded with a plan to partner with Mozilla on Firefox OS in order to increase its low-end smartphone shipments to China, as well as the release of a new high-end waterproof smartphone called Xperia Z. In May, activist shareholder Dan Loeb, the founder and chief executive of hedge fund Third Point, revealed he had acquired around $US1.1 billion in shares in the struggling Japanese electronics giant. Loeb subsequently sent a letter to Sony chief executive Kazuo Hirai arguing the electronics giant should spin off its non-core media assets, including its investments in the music and movie industries, in order to focus on consumer electronics. In a letter to investors sent this week, Loeb commended the result and Hirai's efforts to turn Sony around, but says the company needs to do more to boost shareholder value.