Apple’s (AAPL.NASDAQ) CEO Tim Cook paid a visit to Beijing this week, as the firm announced plans for “greater investment” in its second-largest market after the US, Bloomberg reported. “China is very important to us and we look forward to even greater investment and growth here,” said Carolyn Wu, an Apple spokeswoman. Cook said earlier this year that Chinese demand for the iPhone was “staggering” and that Apple “didn’t bet enough,” though store openings have lagged behind a company forecast set two years ago. “The challenge now is to extend the successful retail model they have in the US to China. Now they are really still in a test phase. It’s time to take it broader,” said David Wolf, head of marketing strategy consulting firm Wolf Group Asia. Apple signed China Telecom (CHA.NYSE, 728.HKG), as the second carrier for its iPhone this month, in addition to China Unicom (CHU.NYSE, 600050.SH, 0762.HKG), doubling its potential customer base.