The temperature coefficient of resistance for a wire is . . .

Question : The temperature coefficient of resistance for a wire is 0.00125/°C. At 27°C its resistance is 1 ohm. The temperature at which the resistance becomes 2 ohm is 

a) 1154 K

b) 1100 K

c) 1400 K

d) 1127 K

Doubt by Sonali & Parish

Solution : 

Here
α = 0.00125/°C

T1 = 27°C

R1 = 1Ω

T2 = ?

R2 = 2Ω

We know, 

α = (R₂-R₁)/R₁(T₂-T₁)
0.00125 = (2-1)/(1)(T₂-27)
125/100000 = 1/(T₂-27)
5/4000 = 1/(T₂-27)

1/800 = 1/(T₂-27)
T₂-27=800
T₂ = 800+27
T₂ = 827°C
T₂ = 273+827
T₂ = 1100 K

Hence, b) would be the correct option.