For the couple of decades, China has been grown around 10%/year, but recently the growth has fallen

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For the couple of decades, China has been grown around 10%/year, but recently the growth has fallen to 6%. US, for instance, has been growing at around 2%/year. Why slowdown in china would be a concern for US? If prices in China fall because of slowdown, would it hurt or help US? Explain.