2. The following figure shows a triangulation station O from which the horizontal directions di, d2, and d3 were measured to three stations A, B, and C, respectively, with the following observations: dl = 45 15'25", d2 = 7525'35", d3= 11535'45" CL = 200 0 2 0 arc sec 002 204 ch 21 C Calculate the estimates of the two horizontal angles ai and a2 and their variance-covariance matrix. Discuss the degree of correlation between the two angles.