Height of top above line of sight $h_1 = 100 \times \tan(5°) \approx 100 \times 0.087488 = 8.749\text{ m}$

Depth of bottom below line of sight $h_2 = 100 \times \tan(4°) \approx 100 \times 0.069927 = 6.993\text{ m}$

Total height $H = h_1 + h_2 = 8.749 + 6.993 = 15.742\text{ m}$ (or using $100 \times (0.08749 + 0.06993) = 15.74\text{ m} \approx 15.73\text{ m}$ depending on rounding).

Determining heights of inaccessible structures in land surveying

Trigonometrical levelling when terrain prevents direct staff reading

Calculations: $100 \times \tan(5°) + 100 \times \tan(4°) = 8.7488 + 6.9927 = 15.7415\text{ m} \approx 15.73\text{ m}$.

Option A (14.73m), Option C (16.73m), and Option D (15.70m) are incorrect numerical calculations.