Erythrocytes Membrane

I don't understand the following. Please help me. I'm more interested in the explanation if you can. Thank you!

 1) Membrane lipids from 4.74*109 erythrocytes form a monolayer of 0.89 m2 in water.  The surface area of an average erythrocyte is ~ 100 mm2.  Show that the membrane is a bilayer.

2)
a. How many moles of K+ will diffuse across the erythrocyte membrane in one minute under the following conditions:
[K+]in = 100 mM
[K+]out = 15 mM
Surface Area of erythrocyte: 100 mm2 = 100*10-12 m2
Permeability P of K+ = 2.4*10-10 cm-sec-1

b. If the erythrocyte volume is 100 mm3, what percent of the internal K+ willl leak out in 1 minute?