Concept:
According to H.I method or Collimation method,
H.I = R.L + B.S
R.L = H.I – (B.S/F.S)
The Arithmatic check is given by,
ΣB.S - ΣF.S = Last R.L - First R.L
Where,
H.I = Height of instrument, R.L = Reduced level
B.S = Backsight, F.S = Foresight
Calculation:
Using H.I method
ΣF.S. > ΣB.S.
∴ ΣF.S. – ΣB.S. = R.L. of first station – R.L. of last station
∴ ΣF.S. – ΣB.S = 5.645 – 3.085 = 2.56 m
R.L. (last station) = R.L. (first station) – 2.56 = 100.00 – 2.56 = 97.44 m