[Wien] BoltzTrap calculations at fixed temperature

[Hannan.Sadek at uv.es]

Dear All,
If I want to calculate the transport coeffecient at a fixed temperature(300k for example), which way is correct to fix the value of the temperature(300k) in the case.intrans file or to make the calculation over a range of a temperature as usual(50-800k) and select the results corresponding to 300K from the case.trace file. 
Also, What is the difference between the two methods?
Regards
Hannan