For each of the following, either give an example, in _-notation, or explain why it is impossible to do SO: (a) An infinite geometric series such that its first term is 4 and its sum is 10. (b) An infinite geometric series such that its first term is 10 and its sum is 4. DO (c) Two geometric series, _ ak and > bu, that converge but E diverges. k=1 k=1 k=1