4B. The Moore plane Let denote the closed upper half plane {(x, y) | y 0} in R. For each point in the open upper half plane, basic nhoods will be the usual open disks (with the restriction, of course, that they be taken small enough to lie in T). At the points z on the x-axis, the basic nhoods will be the sets {z}A, where A is an open disk in the upper half plane, tangent to the x-axis at z.