plz need solution

x=8

The height at Point X is to be determined by levelling form 3 benchmark locations A, B and C as shown in Figure 1. The observed height differences, the lengths of levelling lines and the heights of benchmarks are given in Table 2. Weighted levelling adjustment is considered. Figure 1 Height of benchmarks Height difference Length (m) (m) (km) HA = 3.420 hi = 3.242 LI =8 Ha = 2.589 h2 = -4.07X He = 4.215 ha = 2.448 La =6 HD = 0.25X ha =-6.405 LA=9 Table 2 (a) Construct a system of observation equations to estimate the height at Point X. (4 marks) (b) Find the MOST probable height of Point X. (10 marks) (c) What are the residuals of each of the height differences? (8 marks) (d) Calculate the reference standard deviation of the levelling adjustment