Solve the all parts of given problem:
Problem: Currently the annual growth rate of the US (Gross National Product) is about 2%, while the GNP of China is growing 7% annually. At this time the US GNP is roughly twice as large as that of China. Assume these growth rates will persist.
Part A: In how many years will the Chinese GNP double?
Part B: In which year will the two countries' GNPs be equal to each other?
Please show the work for the calculation so I can understand what I'm doing. Thanks!