Circle c₁ passes through points A(1,2) and B(3,8). The centre C of circle c₁ is on the x-axis.

a) Compute the x-coordinate of centre C.

c₂ is the circle with equation x² + y² - 2x - 4y = 0. Line m is the tangent line to circle c₂ in the origin O(0,0).