When we use a sum of rectangular areas to approximate the area bounded by the curve y=f(x), the x-axis and the vertical lines at x = a and x=b, what do a, b, Ax, and n represent? What does Ax represent? Choose the correct answer below. O A. Ax represents the left endpoint. OB. Ax represents the number of intervals. OC. Ax represents the width of each interval. OD. Ax represents the right endpoint. What does n represent? Choose the correct answer below. O A. n represents the width of each interval. OB. n represents the number of intervals. OC. n represents the right endpoint. OD. n represents the left endpoint. What does b represent? Choose the correct answer below. O A. b represents the number of intervals. OB. b represents the right endpoint. O c. b represents the left endpoint. OD. b represents the width of each interval. What does a represent? Choose the correct answer below. O A. a represents the left endpoint. ОВ. a represents the number of intervals. OC. a represents the right endpoint. OD a represents the width of each interval.