Charges `5.0 xx ^(-7) C and 1.0 xx 10^(-7) C` are
held fixed at the three cornners A, B, C of an equilateral
. charge at C due to the rest two.

Explanation

Let's solve the problem step by step.

### Step 1: Identify the Charges and Distances
Given:
- Charge at A, \( q_A = 5.0 \times 10^{-7} \, \text{C} \)
- Charge at B, \( q_B = -2.5 \times 10^{-7} \, \text{C} \)
- Charge at C, \( q_C = 1.0 \times 10^{-7} \, \text{C} \)
- Side of the equilateral triangle, \( d = 5 \, \text{cm} = 0.05 \, \text{m} \)
...