Let's find the molar conductivity of Acetic Acid (CH3COOH). We cannot measure it directly because it is a weak electrolyte. Step 1: Get the values for strong electrolytes: Sodium Acetate (CH3COONa), Hydrochloric acid (HCl), and Sodium Chloride (NaCl). Step 2: Write the law: Lambda(CH3COOH) = Lambda(CH3COONa) + Lambda(HCl) - Lambda(NaCl). Step 3: Imagine the ions: (CH3COO- + Na+) + (H+ + Cl-) - (Na+ + Cl-). Step 4: Watch the Na+ and Cl- cancel out. Step 5: You are left with (CH3COO- + H+), which is exactly Acetic Acid. If CH3COONa is 91, HCl is 426, and NaCl is 126, then: 91 + 426 - 126 = 391. The answer is 391 units.