The inspiratory capacity, functional residual capacity and residual volume of a person are 3,500 mL, 2,300 mL and 1,200 mL, respectively. What is his vital capacity? 

IC = 3,500 mL; FRC = 2,300 mL; RV = 1,200 mL; VC = ?

FRC = ERV + RV

2,300 mL = ERV + 1,200 mL

ERV = 2,300 mL - 1,200 mL = 1,100 mL

VC = IRV + TV + ERV = IC + ERV

= 3,500 mL + 1,100 mL = 4,600 mL