A. Why do the diameters of bones across species scale with their lengths to the 3/2 power?<p><br>

B. A ventilation system steadily blows air at temperature 18 C into a room.
   (a) If there are enough people in the room to raise the temperature to a steady-state
       value of 24 C, by what fraction is the air leaving the room depleted in oxygen?
   (b) On what timescale should the vents completely replace the air, to prevent the temperature
       from rising above 24 C?<p><br>


C. Knowing that the angular resolution of the human eye at the center of its field of view (fovea) is
   diffraction-limited, estimate the surface density (number per unit area)
   of light-sensitive cells (cones) at the fovea.
   For reference, pupil sizes range from 0.2 to 0.4 cm. Estimate also the pixel sizes
   of TVs.