d) (2 points) Find a formula for the height of the k'th rectangle, f(x). (The only variables appearing in your expression should be k and n.) e) (3 points) Write the Riemann sum for this area approximation in Sigma notation. (Do not evaluate the sum here. Your answer should include the variable n and the index variable k.) Sum in Sigma Notation: f) (6 points) Evaluate the sum from part (e) above. (The only variable in your answer should be n. Use the summation formulas from this section in the textbook where appropriate.) Evaluated Sum: