A liquid with a density of 900 kg/m³ flows straight down in a 6-cm-diameter cast iron pipe. Estimate the pressure rise over 20 m of pipe if the average velocity is 4 m/s. Assume n=8×10⁶ m² /s. What is the estimated pressure rise (in Pa)?

A) 6000
B) 8000
C) 10000
D) 12000