Here is a goal: How long should I cook butter cookies?

How would you accomplish this goal?

Select from the following.
 - You should bake butter cookies in the oven for 12-15 minutes at 170F;
 - You should bake butter cookies in the oven for 12-15 minutes at 170C.;
You should bake butter cookies in the oven for 12-15 minutes at 170C.