Water at a pressure of 4.80 atm at street level flows into an office building at a speed of 0.80 m/s through a pipe 6.80 cm in diameter. the pipes taper down to 2.50 cm in diameter by the top floor, 29.0 m above. calculate the water pressure in such a pipe on the top floor.

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Ohm's law tells you that i = v/r where v is equivalent voltage and r is equivalent resistance of the circuit
since all circuits have the same voltage, your question is really asking which circuit has the lowest total resistance, since the lower the resistance, the higher the current
circuit a has a resistance of 5 ohms; circuit c is in series so has a resistance of 10 ohms; circuit b is in parallel and therefore has a resistance of 2.5 ohms (review your notes on adding resistances in parallel and series); therefore b has the highest current