Limiting molar conductivity of ${\text{NH}}_4\text{OH}$ (i.e., ${\Lambda }_m^{\circ }({\text{NH}}_4\text{OH})$) is equal to:

1. A
   ${\Lambda }_m^{\circ }({\text{NH}}_4\text{Cl})+{\Lambda }_m^{\circ }(\text{NaOH})-{\Lambda }_m^{\circ }(\text{NaCl})$
2. B
   ${\Lambda }_m^{\circ }({\text{NH}}_4\text{Cl})+{\Lambda }_m^{\circ }(\text{NaCl})-{\Lambda }_m^{\circ }(\text{NaOH})$
3. C
   ${\Lambda }_m^{\circ }(\text{NaOH})+{\Lambda }_m^{\circ }(\text{NaCl})-{\Lambda }_m^{\circ }({\text{NH}}_4\text{Cl})$
4. D
   ${\Lambda }_m^{\circ }({\text{NH}}_4\text{OH})+{\Lambda }_m^{\circ }({\text{NH}}_4\text{Cl})-{\Lambda }_m^{\circ }(\text{HCl})$