1. **State the problem:** Find the derivative of the function $r = es$ with respect to $s$. 2. **Recall the formula:** The derivative of a function $r(s)$ with respect to $s$ is denoted as $\frac{dr}{ds}$. 3. **Identify constants and variables:** Here, $e$ is the mathematical constant approximately equal to 2.71828, and $s$ is the variable. 4. **Apply the derivative rule:** Since $e$ is a constant, the derivative of $r = es$ with respect to $s$ is the constant $e$ times the derivative of $s$ with respect to $s$. 5. **Derivative of $s$:** $\frac{d}{ds}s = 1$. 6. **Calculate the derivative:** $$\frac{dr}{ds} = e \times 1 = e$$ 7. **Final answer:** The derivative of $r = es$ with respect to $s$ is $e$.