Correct option is (b) 5.04

The best I can explain: Pitch=\(\frac{πD}{T} \)

D1=\(\frac{PT}{π}=\frac{0.015*60}{π}\) = 0.287 m

Peripheral speed, v=\( \frac{πDN}{60} = \frac{(π*0.287*18)}{60}\) = 2.70 m/s

H.P = \( \frac{F*v}{75}=\frac{140*2.70}{75} \)

H.P = 5.04.