topic: TOPOGRAPHIC SURVEYING
Extracted text: INTERPOLATING CONTOURS ANALYTICALLY. Using a suitable scale, plot a rectangular area 5435 m (length of side AB) by 2795 m (length of side BC). The elevation at the center of the area is 265 m and the elevation of corners A, B, C, and D being 163, 191, 315, and 224 m, respectively. By the analytical method, plot the contours at 20-m interval, Designate contours 200 and 300 as index contours.