Question 7 Not yet Consider the joint density function answered Marked out of f (x, y ) = =xy, Oxx, 0 0 Three such fuses operate independently. Find the joint density of their lengths of life. Select one: O a. f(x1, X2, X3) = 03 O b. f(x1, X2, X3) = e 03 A O c. f(x1, X2, X3) = e 03 O d. e as f(x1, x2, X3) = 03