Answer
a) $10^{7}$ breaths/yr
b) $4000m^{3}$
Work Step by Step
a) Breaths per year = $\frac{1 breath}{4s}\times\frac{3.156\times10^{7}s}{ 1 yr}\approx10^{7} breaths/yr$
b) Assume 0.5L per breath
volume = $8\times10^{6}\times\frac{0.5L}{1 breath}=4\times10^{6}L \times\frac{10^{-3}m^{3}}{1 L}=4000m^{3}$
