Humans evolved in Earth's atmosphere, therefore the pressures interior to the body are relatively close to atmospheric pressure. Because the differences between internal body pressures and atmospheric pressure are so small, individuals have a difficult time gauging the magnitude of atmospheric pressure. Suppose an individual is lying on his stomach with sheets of paper stacked on his back. If each sheet of paper has a mass of 0.00290 kg and is the standard letter size of 8.5 in by 11 in ( 0.216 m by 0.279 m ), how many sheets must be stacked to produce a pressure on his back equal to atmospheric pressure (roughly 101325 Pa )