Without actually values for and N, you're not going to get very far. However:
A. You're literally just plugging in the values you are given. K is dependent on the number of cells before the experiment is conducted, so K can be an odd or an even number: 2N-1 (odd) or 2N (even).
B. Same rationale as above, but you're going to have to use some reasoning. If "n" cells are recorded after the experiment is conducted, how many cells were present before (the answer depends on whether n is even or odd).
Assuming that's ALL the information you are given for the problem, I don't see much more you can do with this.