If (-5 ≤ a ≤ -1) and (1 ≤ b ≤ 3), what is the least possible value of [tex](\frac{1}{a} +\frac{1}{b})(\frac{1}{b} -\frac{1}{a})[/tex]? Express your answer as a common fraction. (if you answer this correctly, you get brainlist. if you answer it incorrectly, I will not give you brainlist)