The net charge within the sphere's surface can be calculated using Gauss's Law, which states that
electric flux = E * A (*where E=electric field, A=area)
which is also equivalent to,
electric flux = (charge in) / (permittivity of free space)
Setting the two equations equal to one another will allow us to solve for Q.
E * A = (charge in) / (permittivity of free space)
charge in = E * A * (permittivity of free space)
given E = -868 N/C (*its negative b/c it is pointing inward)
A = pi*r^2 , where r = 735m, and so A = pi*(735m)^2
permittivity of free space = 8.8542*10^-12 C^2/N*m^2
plugging all this back into the equation we get that:
charge in = (-868 N/C) *(pi*(735m)^2) * ( 8.8542*10^-12 C^2/N*m^2)
which simplifies to:
charge in = -5.2174*10^-8 C = -52.174 nC
The negative charge has a spherically symmetric charge distribution.