Show that the points (5, 5), (6, 4), (-2, 4), and (7, 1) all lie on a circle. What is the equation, center, and radius of this circle?
a. x² + y² = 29
b. x² + y² - 2x - 6y + 30 = 0
c. (x - 3)² + (y - 3)² = 20
d. (x - 2)² + (y - 3)² = 13