(a) y dies after the year of death of x
(b) y dies after x, assuming that times of death over the year of death are equally distributed. Tabulate and compare the results obtained for a few concrete values.
I know how to calculate the probability that x will die in t years and that y will live t+1 years but how do I go further so that y dies after x without a concrete amount of years after x? I started with the probability that x dies in t years and y dies in t+1 years and got this: 
Can I somehow use this to get to a) and b) of this exercise or am i going in the wrong direction?