Consider a pipe that branches out into three parallel pipes and then rejoins at a junction downstream. All three pipes have the same diameters (D = 3 cm) and friction factors (f = 0.018). The lengths of pipe 1 and pipe 2 are 5 m and 8 m, respectively while the velocities of the fluid in pipe 2 and pipe 3 are 2 m/s and 4 m/s, respectively. The length of pipe 3 is

(a) 8 m 

(b) 5 m 

(c) 4 m 

(d) 2 m 

(e) 1 m