(a) Determine the electrostatic potential energy of a system consisting of two charge `7 muC and -2 muC` (and with no external field) placed at `(-9 cm, 0,0) and (9 cm, 0,0)` respectively.
(b) How much work is required to seperate the two charges infinitely away from each other ?
(c) Suppose that the same system of charges is now placed in an external electric field `E = A xx 1//r^(2)`, where `A = 9xx10^(5) C m^(-2)`.
What would the electrostatic energy of the configuration be ?

Explanation

To solve the given problem step by step, we will break it down into three parts as per the question.

### Part (a): Determine the electrostatic potential energy of the system

1. **Identify the charges and their positions**:
- Charge \( Q_1 = 7 \, \mu C = 7 \times 10^{-6} \, C \) is located at \( (-9 \, cm, 0, 0) \).
- Charge \( Q_2 = -2 \, \mu C = -2 \times 10^{-6} \, C \) is located at \( (9 \, cm, 0, 0) \).

...