Problem 731 (difficulty: 6/10)

Find a differentiable function \(\displaystyle f\) which is equal to \(\displaystyle 2x\) for \(\displaystyle x\leq 0\), and equal to \(\displaystyle 3x\) for \(\displaystyle x\geq 1\). Is there a 2 times differentiable function? And a 271 times differentiable function?

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