A horizontal pipe carries oil whose coefficient of viscosity is 0.700 N·s/m2. The diameter of the pipe is 46.0 cm and its length is 51 km.

(a) What pressure difference is required between the ends of this pipe if the oil is to flow with an average speed of 1.5 m/s? Pa
(b) What is the volume flow rate in this case? m3/s
(c) If both the length of pipe and its diameter were each doubled in size, what would the pressure difference required be then? Pa
(d) What is the volume flow rate in this case?
m3/s

I feel i understand how to do b and D but i am unsure if it is correct please can someone help
b)

Cross section area of the pipe

= pi * r^2 = pi * (0.46 / 2)^2

= 0.16619025 m^2

Speed = 1.2 m/s, so the flow rate

1.2 * 0.16619025 = 0.1994283 m^3/s

D.
Would you take the answer from b and multiply by 4 since the diameter is doubled, the cross sectional area is increased by 2^2?