Read this: The location and terrain of Kathmandu have played a significant role in the development of a stable economy which spans millennia. The city is located in an ancient lake basin, with fertile soil and flat terrain. This geography helped form a society based on agriculture. This, combined with its location between India and China, helped establish Kathmandu as an important trading center over the centuries. Kathmandu's trade is an ancient profession that flourished along an offshoot of the Silk Road which linked India and Tibet. From centuries past, Lhasa Newar merchants of Kathmandu have conducted trade across the Himalaya and contributed to spreading art styles and Buddhism across Central Asia. Other traditional occupations are farming, metal casting, woodcarving, painting, weaving, and pottery.

Existing between what two countries contributed to Kathmandu becoming a center of trade?
What is the answer? (If it cannot be answered, return "unanswerable")
India and China