Water flows through a horizontal pipe at a rate of 2.7 {gal/s. The pipe consists of two sections of diameters 4 in. and 2 in. with a smooth reducing section. The pressure difference between the two sections is:

A) Not provided
B) Provided in psi (pounds per square inch
C) Provided in kPa (kiloPascals)
D) Provided in atm (atmospheres)