(i) The slope of the line y = 2x - 7 is 2. The slope of a line perpendicular to this is the negative reciprocal, which is -\frac{1}{2}. Using the point-slope form of a line equation, y - y_1 = m(x - x_1), where m is the slope and (x_1, y_1) is a point on the line, we have:

y - 1 = -\frac{1}{2}(x - 3)

(ii) The midpoint C of AB is calculated as:

C = \left(\frac{3 + (-21)}{2}, \frac{1 + 11}{2}\right) = (-9, 6)

The distance AC is calculated using the distance formula:

AC = \sqrt{(3 - (-9))^2 + (1 - 6)^2} = \sqrt{12^2 + (-5)^2} = \sqrt{144 + 25} = \sqrt{169} = 13