Select the correct formula for functional residual capacity.

Functional Residual Capacity (FRC) = Expiratory Reserve Volume (ERV) - Residual Volume (RV)

Functional Residual Capacity (FRC) = Expiratory Reserve Volume (ERV) + Residual Volume (RV)

Functional Residual Capacity (FRC) = Residual Volume (RV) - Expiratory Reserve Volume (ERV)