Explanation:
Given that,
Length of gold wire, l = 4 m
Voltage of battery, V = 1.5 V
Current, I = 4 mA
The resistivity of gold, 
Resistance in terms of resistivity is given by :

Also, V = IR
So,

A is area of wire,
, r is radius, r = d/2 (diameter=d)

Out of four option, near option is (C) 17 μm.
(t) = 2t = 1.22 sec. I believe ...
The answer should be C. In this question
Answer: The correct answer is C.
2/10 is simplified to 1/5, that is the factor that changes.
Given that:
μ = 36
<span>σ = 3
</span>
<span>Standardize x to z = (x - μ) / σ </span>
<span>P( 39 < x < 42) = P[( 39 - 36) / 3 < Z < ( 42 - 36) / 3] </span>
<span>P( 1 < Z < 2) = P( x < 2) - P( x < 1)
= 0.9772 - 0.8413
= 0.1359 </span>
<span>(0.1359)(30)
= 4.0777
= 4 days</span>