Consider the following hypothetical problem. Potassium ions have a concentration of 115 x 10 ^-3 mol/liter inside the cell and 4.5 x 10 ^-3 mol/liter outside the cell. The cell wall has a channel through which the potassium ions can travel and it is 25.0 nm in length and 4.00 nm in diameter. Take the diffusion coefficient of potassium to be 3.00 x 10 ^-9 m ² /s.

A) What is the difference in concentration, Δc across the cell wall in molecules/m ³ ?

B) What is the cross-sectional area of the potassium channel?

C) What is the rate of molecule transfer of the potassium ions?