Right answer is (a) hf = f* (L/(s *d)) * ((1-e)/e^3) * (v^2/g)
The best I can explain: The expression of the Carmen equation is given by hf = f* (L/(s *d)) * ((1-e) /e^3) * (v^2/g) where hf =head loss, d= diameter of pipe. L= length of pipe and v=approach velocity.