It should be such that the sum is equal to 1.p0 = p1 = a, Pk = (1-2a)2^–(a-1) (k >= 2)
Question 2 you need to provide the table as well.
But anyway both question are very elementary and standard, no tricky thing at all. Directly apply the definition of conditional probability is ok.
So show us your effort when you have any further question and come back.