Please see attached question.

20. The sphere, with "lines" interpreted as great circles, is not a model of neutral geometry. Here is a proposed construction of a rectangle on a sphere. Let a, / be two circles of longitude and let them intersect the equator at A and D. Let y be a circle of latitude in the northern hemi- sphere, intersecting o and B at two other points, B and C. Since circles of latitude are perpendicular to circles of longitude, the quadrilateral with vertices ABCD and sides the ares of c, y, and / and the equator traversed in going from A north to B east to C south to D west to A should be a rectangle. Explain why this construction doesn't work