In an external focussing tacheometer the fixed hairs interval is 5 mm, the focal length of the objective lens is 25 cm and the distance of the vertical axis of the instrument from the optical centre of the objective lens is 15 cm. The constants of the tacheometer will be
1
30, 0.15
2
30, 0.40
3
50, 0.25
4
50, 0.40