A rancher wants to fence off his four-sided plot of flat land, as shown in the figure. He measures the first three sides, labeled as A, B, and C, where A=4.79 km, B=2.59 km, and C=2.79 km, and then correctly calculates the length and orientation of the fourth side D.

part a. What is the length of the vector D in kilometers?

part b. What is the orientation of the vector D, in degrees west of south?