Answer:
diameter = 50 units
Explanation:
the diameter(d) of a circle is twice the radius (r)
the radius is the distance from the centre to a point on the circle.
to calculate r use the distance formula
r =

with (x₁, y₁ ) = (3, 2 ) and (x₂, y₂ ) = (10, 26 )
r =

=

=

=

= 25
Then
diameter d = 2 × r = 2 × 25 = 50 units