Please choose the correct solution to the question: How to shape an old sawzall blade into a knife blade.

Solution1: Hold the sawzall blade by the back edge and carefully grind off all the teeth with a belt grinder. Hold the blade at a 20 degree angle and sharpen one side, flip over and sharpen the other side.

Solution2: Hold the sawzall blade by the back edge and carefully grind off all the teeth with a belt grinder. Hold the blade at a 90 degree angle and sharpen one side, flip over and sharpen the other side.

Answer format: solution1/solution2
Answer: solution1