Efficiency of a screw jack is given

Efficiency of a screw jack is given by (where α
α
= Helix angle and φ
φ
= Angle of friction)
A. tan(α+φ)tanα
tan⁡(α+φ)tan⁡α
B. tanαtan(α+φ)
tan⁡αtan⁡(α+φ)
C. tan(α−φ)tanα
tan⁡(α−φ)tan⁡α
D. tanαtan(α−φ)
tan⁡αtan⁡(α−φ)
Answer: Option B