Parametric Equations: Values of a, b & k for Circles A, B & C

[ada0713]

Homework Statement

Each of the three circles A, B and C of the figure below can be parameterized by equations of the form
x = a + k cos t, y = b + k sin t, 0 ≤ t ≤ 2.
What can you say about the values of a, b and k for each of these circles?
(figure attached below)

The Attempt at a Solution

A: a and b are both zero because the circle is at the origin, k is 5 b/c the radius is 5
B: Since the circle moved up by 5, b is 5 and a is zero, k is agian 5 since the radius is 5
C: The circles's radius is 2\sqrt{10} and it moved right and down by 10.
Thus, a is 10 and b is -10, and k is 2\sqrt{10}

Above is how i came up with the answer but I'm not 100% sure.
Did I do it right, or is somthing wrong?

 

[rock.freak667]

Well since the picture is pending approval, I would suggest to put the equation into Cartesian form and check the radius,centres and etc