The salinity of the oceans changes with latitude and with depth. In the tropics, the salinity increases on the surface of the ocean due to rapid evaporation. In the higher latitudes, there is less evaporation and rainfall causes the salinity to be less on the surface than at lower depths. The function given by S(x) = 31.5 + 1.1 log(x + 1) models salinity to depths of 1000 meters at a latitude of 57.5°N. The input x is the depth in meters and the output S(x) is in grams of salt per kilogram of seawater. 

(a) Evaluate S(500). Interpret your result. 

(b) Graph S. Discuss any trends. 

(c) Find the depth where the salinity equals 33.