4-7. Given the following cumulative distribution function, find:

(a) f (0)

(b) f (2)

(c) f (3)

(Hint: f (Xi) = F(Xi) − F(Xi − 1).)

F(X) =

⎧⎪⎪⎪⎪⎪⎨

⎪⎪⎪⎪⎪⎩

0, X < 0;

1 2, 0≤ X ≤ 2;

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, 2≤ X ≤ 3;

1, X ≥ 3.