For Problem 6.49, hLoss is expressed in feet, L and D in inches, V in (ft /s), and g in...

For Problem 6.49, h_Loss is expressed in feet, L and D in inches, V _in (ft /s), and g in (ft /s²). What is the appropriate unit for the friction factor f ?

Problem 6.49:

The head loss due to flow of a fluid inside a pipe is calculated from friction factor, L is pipe length (m), D is pipe diameter (m), V is average flow velocity (m/s), and g is the acceleration due to gravity (m/s²). What is the appropriate unit for friction factor f ?