(a) since the flow rate is proportional to the pressure difference, show that Poiseuille's law can be written in the form $\Delta P=I R,$ where $I$ is the volume flow rate and $R$ is a constant of proportionality called the fluid flow resistance. (Written this way, Poiseuille's law is analogous to Ohm's law for electric current to be studied in Chapter $18: \Delta V=I R,$ where $\Delta V$ is the potential drop across a conductor, $I$ is the electric current flowing through the conductor, and $R$ is the electrical resistance of the conductor.) (b) Find $R$ in terms of the viscosity of the fluid and the length and radius of the pipe.