How exactly do you solve this electrical problem?

Hello, I have problems with the following task:

I have the following formula:

What I don’t understand now, however, is:
The formula assumes a resistance of R20 at a temperature of 20°, but in my task I have a temperature of 10°. Can I still just use 2.5 ohms for R20?

There is also a p20 given in the task, do I have to do anything with it?

Thanks in advance for your help!:)