The PDFS of two statistically independent random variables X and Y are shown below. The PDF of the sum Z-X+Y can found as fx(x)= 3 exp(-3x) u(x) fr(y) = 3 exp(-3y) u(y) O a. 4z exp(-2z) U(z) O b. 25z...

Extracted text: The PDFS of two statistically independent random variables X and Y are shown below. The PDF of the sum Z-X+Y can found as fx(x)= 3 exp(-3x) u(x) fr(y) = 3 exp(-3y) u(y) O a. 4z exp(-2z) U(z) O b. 25z exp(-5z) u(2) O c. 3z exp(-3z) u(z) O d. 9z exp(-3z) u(z)