Answer: 0.0031 in²
Step-by-step explanation: 
Formula: CSA = CSA = πD²  / 4  = 0.785 x D²
in which,
CSA = cross-sectional area of the wire, (in²)
D = outside diameter of the wire, (in)
π/4 = 0.785, a constant value 
* (3.14 / 4 = 0.785) - this will always be a <em><u>constant value.</u></em>
There are two ways to find the CSA of a wire.
1.         πD² / 4 
           3.14(0.0625²) / 4 
           First multiply or square the diameter which is 0.0625
           0.0625 x 0.0625 = 0.00390625
           Second multiply 3.14 which is pi times the squared diameter 
           3.14 x 0.00390625 = 0.012265625
           Last divide by 4
           0.012265625 / 4 = 0.0030664062 in² 
           Round off and you will get 0.0031 in²
2.        0.785 x D²
           whereas, 0.785 is <u><em>always a constant</em></u> of π divided by 4
           0.785 x 0.0625²
           First multiply or square the diameter which is 0.0625
           0.0625 x 0.0625 = 0.00390625
           Last multiply the constant value of 0.785 by the value squared
           0.785 x 0.00390625 = 0.0030664062 in²
           Round off and you will get 0.0031 in²
* Hint - it is easier to remember that the constant value is 0.785