Option 1: 50%

This option suggests that the increase in length is 50%. However, this is incorrect. The increase in length cannot be 50% because the wire is being stretched and its radius is reduced by 20%.

Option 2: 56-25%

This option suggests that the increase in length is 56-25%. This can be simplified to 31%. This means that the length of the wire increases by 31%.

Option 3: 62-25%

This option suggests that the increase in length is 62-25%. This can be simplified to 37%. This means that the length of the wire increases by 37%.

Option 4: 75%

This option suggests that the increase in length is 75%. However, this is incorrect. The increase in length cannot be 75% because the wire is being stretched and its radius is reduced by 20%.

The correct answer is option 2, which states that the value of increase in length is 31%. This means that the length of the wire increases by 31%.