Let the random variables x and y have joint pdf as follows: f x( , y c ) , = + x y 0 < < x y < < 1 2 , 0 1 a. find the value of constant c. b. find the marginal densities of x and y. c. are the random variables x and y independent? d. find the conditional pdf ’s ( | ) 1f x y and ( | ). 2f y x e. find e x( ) and e y( ). f. find var x( ) and

Isuck at math ; ^; m a student solved this problem and said the answer is 3 feet. chase had a roll of ribbon that contained 7 7/8  feet of ribbon. he cut off one piece that was 3 5/8  feet long and another piece that was 1 1/4  feet from the roll. how much ribbon was left on the roll? is the student's answer reasonable? yes, the answer is reasonable. no, the answer is not reasonable. it should be about 2 feet. no, the answer is not reasonable. it should be about 13 feet. no, the answer is not reasonable. it should be about 4 feet.