Use the partial fraction expansion method to find the inverse z-transform X(z) = z / ((z-0.2)(z-0.4)):

a. e⁰.2n + e⁰.4n
b. 1/0.2 + 1/0.4
c. 0.2ⁿ + 0.4ⁿ
d. 1/(z-0.2) + 1/(z-0.4)