Find the the distribution function of random variable Z and its expected value

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Point P is the midpoint of a line segment AB whose length is 1. Let point T1 be a random point between points A and P, and point T2 be a random point between points A and B. The random variable Z is the length of the line segment T1T2. Find the distribution function of Z and its expected value.

My current progress:

I will define the length of line segment AT1 as X and AT2 as Y. Which leads to Z=|Y-X|.

So there are 2 cases:

1) X > Y

2) Y > X

Now using graphs I find the limits of Z.

(I'd include a graph but im not allowed because the lack of reputation)

For the first case(X > Y) I get the limits of Z as [0, 0.5], and for the second case(Y > X) I get the limits of Z as [0.5, 1].

The funtion for the first case is Y=X-Z, and for the second is Y=X+Z

Now comes the part where I need to define the limits of the mariginal distribution which I am currently stuck on.