Calculate ${\Lambda }_{\text{HOAc}}^{\infty }$ using the following molar conductances at infinite dilution at $25^{\circ }\text{C}$:

According to Kohlrausch's Law of Independent Migration of Ions:
$${\Lambda }_{\text{HOAc}}^{\infty }={\Lambda }_{{\text{H}}^{+}}^{\infty }+{\Lambda }_{{\text{OAc}}^{-}}^{\infty }$$
We can obtain this from the given electrolytes:
$${\Lambda }_{\text{HOAc}}^{\infty }={\Lambda }_{\text{HCl}}^{\infty }+{\Lambda }_{\text{NaOAc}}^{\infty }-{\Lambda }_{\text{NaCl}}^{\infty }$$
Calculation:
$${\Lambda }_{\text{HOAc}}^{\infty }=426.2+91.0-126.5=517.2-126.5=390.7{\text{S cm}}^2{\text{mol}}^{-1}$$