19. Iridium (atomic mass \( 192.2 g / mol ) \) structure has density of \( 22.4 g / cm ^{3} \). The volume of a single unit cell is
(A) \( 2.7 \times 10^{-23} cm ^{3} \)
(B) \( 3.7 \times 10^{-23} cm ^{3} \)
(C) \( 4.7 \times 10^{-23} cm ^{3} \)
(D) \( 5.7 \times 10^{-23} cm ^{3} \)