The Henry's Law Constant for Oxygen Dissolving in Blood Is $\times$

The Henry's law constant for oxygen dissolving in blood is 3.74 $\times$ 10^-2 mol/L .atm at body temperature,37 ^$\circ$ C.Calculate the molar concentration of oxygen in blood for an alpine climber where the atmospheric pressure is 0.45 atm.The mole fraction of oxygen in air is 0.209.

A) 7.8 $\times$ 10^-3 M
B) 3.5 $\times$ 10^-3 M
C) 2.3 $\times$ 10^-2 M
D) 1.3 $\times$ 10^-2 M
E) 0.11 M