The relationship between the US and China is fraught with difficult and even dangerous problems. But there are also deep cultural ties that represent possibilities for peace. That’s the perspective of world renowned cellist Yo-Yo Ma. In the final installment of our summer series, “Face Off: The US versus China,” we hear how the Chinese-American musician convinces himself to be optimistic in the face of cruelty. “Face Off” is a podcast produced by veteran journalist Jane Perlez.