The rectangles in the graph below illustrate a left endpoint Riemann sum for $\displaystyle f(x) = \frac{-x^{2}}{4}+2x$ on the interval $\lbrack 3, 7 \rbrack$.
The value of this left endpoint Riemann sum is , and this Riemann sum is [select an answer] an overestimate of equal to an underestimate of there is ambiguity the area of the region enclosed by $\displaystyle y = f(x)$, the x-axis, and the vertical lines x = 3 and x = 7.

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The rectangles in the graph below illustrate a right endpoint Riemann sum for $\displaystyle f(x) = \frac{-x^{2}}{4}+2x$ on the interval $\lbrack 3, 7 \rbrack$.
The value of this right endpoint Riemann sum is , and this Riemann sum is [select an answer] an overestimate of equal to an underestimate of there is ambiguity the area of the region enclosed by $\displaystyle y = f(x)$, the x-axis, and the vertical lines x = 3 and x = 7.