The three-dimensional (X, Y, Z) coordinates in meters of vertexes A, B, and C in Figure 18.14

Question:

The three-dimensional (X, Y, Z) coordinates in meters of vertexes A, B, and C in Figure 18.14 are (5412.456, 4480.621, 248.147), (5463.427, 4459.660, 253.121) and (5456.081, 4514.382, 236.193), respectively. What are the coordinates of the intersection of the 250-m contour with side AB? With side BC?