Answer:
The length of the second copper wire is 1250.4 feet.
Explanation:
The length of the first wire, 
 = 750 feet.
 = 750 feet.
Resistance of the first wire, 
 = 1.893 Ω
 = 1.893 Ω
The length of the second wire = 

Resistance of the second wire, 
 = 3.156 Ω
 = 3.156 Ω
The length of the second wire can be determined by the relation;
 =
 = 

 =
 = 

 =
 = 

 = 

 = 1250.3962
 = 1250.3962
 = 1250.4
The length of the second copper wire is 1250.4 feet.