Single/multi-choice problem: Which of the following solutions is better for the following goal:
How to harden leather

Pick from: -- Heat the oven to 400 degrees. Then put the shaped leather in the oven for about 10 minutes.. -- Cool the leather to 40 degrees. Then put the shaped leather in the refrigerator for about 10 minutes..
Heat the oven to 400 degrees. Then put the shaped leather in the oven for about 10 minutes.