I had no problem solving number 13 Number 4 is saying I calc

I had no problem solving number 1-3. Number 4 is saying I calculated something else and I cannot figure it out. Please help me solve number 4 and number 5.

An infinite sheet of charge is located in the y-z plane at x = 0 and has uniform charge density 1 = 0.69 C/m-. Another infinite sheet of charge with uniform charge density 2 =-0.15 C/mz is located at x-c-20 cm.. An uncharged infinite conducting slab is placed halfway in between these sheets ( i.e., between x-8 cm and x = 12 cm). al 2 af2 af2 1) what is EXP), the x-component of the electric field at point P, located at (x,y) = (4 cm, 0)? 47457 N/C Submit Your submissions: 47457. Computed value: 47457 Feedback: Your answer has been judged correct; the exact answer is: 47500.8408. Submitted: Wednesday, March 9 at 11:47 AM 2) What is oa, the charge density on the surface of the conducting slab at x - 8 cm? -4.1999445E- HC/mt Submit Your submissions: -4.1999445E-1 Computed value: -4.1999445E-1 Feedback: Your answer has been judged correct; the exact answer is: -0.42. : Submitted: Wednesday, March 9 at 11:55 AM

Solution

4) potential difference:

VS - Vp = -E*d

= -47457*(0.16 - 0.04 - 0.04)

= -3796.56 V

5) electric field is,

Ex(T) = (sigma1 - sigma2)/(2*epsilon)

= (0.69 - 0.15)*10^-6/(2*8.854*10^-12)

= 30494.69 N/C