1. The problem asks whether the estimate from part (a) is an underestimate or an overestimate and to provide a reason. 2. Typically, when estimating values using methods like linear approximation or rounding, the nature of the function (concave up or down) determines if the estimate is an underestimate or overestimate. 3. If the function is concave up (its second derivative is positive), a linear approximation underestimates the actual value. 4. Conversely, if the function is concave down (its second derivative is negative), the linear approximation overestimates the actual value. 5. Therefore, to answer the question, identify the concavity of the function used in part (a). 6. If the function is concave up, the estimate is an underestimate because the tangent line lies below the curve. 7. If the function is concave down, the estimate is an overestimate because the tangent line lies above the curve. 8. Without the specific function from part (a), the general reasoning is that the estimate's nature depends on the function's concavity at the point of approximation. Final answer: The estimate is an underestimate if the function is concave up at the point of approximation, and an overestimate if it is concave down, because the tangent line used for estimation lies below or above the curve respectively.