The Current in a Wire Is Measured at 1 $\times$ 10^-3 /°C

The current in a wire is measured at 1.0 A when the wire is at 20.0°C. As the wire heats up to 80°C, the current drops to 0.77 A while the voltage remains constant. The temperature coefficient of resistance of the material is

A) 0.8 $\times$
10^-3 /°C.
B) 1.0 $\times$
10^-3 /°C.
C) 5.0 $\times$
10^-3 /°C.
D) 8.0 $\times$
10^-3 /°C.