Nour drove from the dead sea up to amman, and her altitude increased at a constant rate. When she began driving, her altitude was 400meters below sea level. When she arrived in amman 2 hours later, her altitude was 1000 meters above sea level. Let a(t), left parenthesis, t, right parenthesis denote nour's altitude relative to sea level a (measured in meters) as a function of time t (measured in hours).