Answer:

Step-by-step explanation:
The resistance of a metal rod is given by

where
is the resistivity
L is the length of the rod
A is the cross-sectional area
The resistivity changes with the temperature as:

where in this case:
is the resistivity of silver at

is the temperature coefficient for silver
is the current temperature
Substituting,

The length of the rod changes as

where:
is the initial length at

is the coefficient of linear expansion
Substituting,

The cross-sectional area of the rod changes as

So, substituting,

Therefore, if the initial resistance at 21.0°C is

Then the resistance at 180.0°C is:
