Katy tried to find the derivative of $10x+3$ using basic differentiation rules. Here is her work: $\begin{align} &&&\phantom{=}\dfrac{d}{dx}(10x+3) \\\\ \text{Step 1} &&&=\dfrac{d}{dx}(10x)+\dfrac{d}{dx}(3) \\\\ \text{Step 2} &&&=\dfrac{d}{dx}(10x)+0 \\\\ \text{Step 3} &&&=10\dfrac{d}{dx}(x) \\\\ \text{Step 4} &&&=10\cdot 1 \\\\ \text{Step 5} &&&=10 \end{align}$ **At which step did Katy make a mistake, if at all?** [[☃ radio 1]]