As altitude increases, the available amount of oxygen to sustain mental and physical alertness decreases with the overall air pressure, though the relative percentage of oxygen in air, at about 21%, remains practically unchanged up to 21,000 metres (70,000 ft).
  State legislators in Texas (both representatives and senators) make a salary of $7,200 per year.
Among other duties, representatives introduce bills and resolutions, offer amendments and serve on committees. The number of representatives with full voting rights is 435, a number set by Public Law 62-5 on August 8, 1911, and in effect since 1913. The number of representatives per state is proportionate to population. Article 1, Section 2 of the Constitution provides for both the minimum and maximum sizes for the House of Representatives.