Fill in the blanks to make the following statements correct.

a. On a graph with Y on the vertical axis and X on the horizontal axis, the slope of a straight line is calculated as ___________.

b. In the equation the vertical intercept is ___________, Y and X ___________ are related to each other, and the slope of this linear function is ___________.

c. In the equation Y = 500 + 4X the vertical intercept is ___________ , Y and X are related to each other, and the slope of this linear function is ___________.

d. For a non-linear function, the slope of the curve at any specific point is measured as the slope of a straight line drawn ___________ to that point.

e. On a graph of a non-linear function with either a minimum or a maximum point, the slope at the minimum or maximum is ___________, meaning that the marginal response to a change in the independent variable is ___________.