Imagine a map of the United States in the usual position. The positive x-direction is east and the positive y-direction is north. Suppose that the units of x and y are miles, and that Los Angeles, California, has coordinates (0,0). (Several approximations are involved here. The earth's surface is not flat and Los Angeles occupies more than a single point.) Let T(x,y) be the temperature, in degrees Celsius, at the location (x,y), at noon, Central Standard Time, on January 1, 2005. (i) What does it mean in weather language (practical terms) to say that T(0,0) = 15? (ii) What do the or contours of T mean in weather language (in practical terms)? (iii) Would you expect, as a rule, for level curves of T to run north-and-south (vertically), or east-and-west (horizontally)? Why?