I am struggling with the question below. I have solutions for parts a and b using the equations C = E_0EA/d and Q=CV, but I don't think these are...

I am struggling with the question below. I have solutions for parts a and b using the equations C = E_0EA/d and Q=CV, but I don't think these are giving me the correct solution. I think the E-feild in part C can be calculated by V/d, but then I end up not using E=78 given for the liquid core at any point in my solution and it concerns me.