physics---Gauss's Law1

(a) Electric flux = (4.5x10^-3) x (pi x 0.11^2) J.m/C = 1.71 x 10^-4 Jm/C

(b) Imagine the proton is inside the centre of a cube with each side of length d.
Total electric flux given out by the proton = e/p
where e is the proton charge (= 1.6x10^-19 C)
p is the permittivity of free space (= 8.85x10^-12 F/m)

Hence, total flux = 1.6x10^-19/8.85x10^-12 Jm/C = 1.81 x 10^-8 Jm/C
Because there are 6 sides in a cube, by symmetry, flux through each side
= total flux/6 = 3.02x10^-9 Jm/C