Determine whether or not each of the following pairs of random variables are independent:
(a) The random variables described in Exercise 1;
(b) The random variables described in Exercise 2;
(c) The random variables described in Exercise 3;
(d) The random variables described in Exercise 4.
Exercise 1
For positive constants and , a pair of random variables has a joint PDF specified by
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Exercise 2
For positive constants ,a , b, c and positive integer , a pair of random variables has a joint PDF specified by
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Exercise 3
For some integer L and constant c, two discrete random variables have a joint PMF given by
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(a) Find the value of the constant c in terms of L .
(b) Find the marginal PMFs, 
(c) Find 
Exercise 4
Two discrete random variables have a joint PMF as described in the following table.
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