The task at hand is solved pretty easily using the Pythagorean theorem and using the data provided under Condition 1.
I attach the image of the geometrical structure that's helpful - but basically, we should draw three radiuses from the centre: two to the tangent points of the circle and one leading straight to A.
As it's quite easy to notice from the drawing, if we know the coordinates of A, we also know that BC equals to radius minus A's height (so, BK - 8, or R - 8).
Same applies to the horizontal radius: CH is of course parallel and equal to the radius, so AC = HC - A's X-coordinate, or AC = HC - 4 = R - 4.
Now let's look at the triangle ABC:
\(AB^2 = AC^2 + BC^2\\
R^2 = (R-4)^2 + (R-8)^2\\
R^2 = R^2 + 16 -8R + R^2 + 64 - 16R\\
R^2 = 2R^2 - 24R + 80,\)
or we get a simple quadratic equation:
\(R^2 - 24R + 80 = 0\)
It's easy to distinguish, using the Vieta's formulas, that the roots are 4 and 20. So, we know that there are two options for the radius.
And now it looks tempting to use the Condition 2, which tells us to choose the option above 15, which is 20.
However, this condition is excessive, because if the radius equals to 4, than the point A would be placed in a completely different part of the circle - to be precise, on the top on the diameter drawn from point K in my scheme.
This is not possible for two reasons:
(1) we were given the drawing where the placement of A is quite obvious; and
(2) we actually obtained the equation using A the way it's drawn - so if it's in any other place, the whole geometrical solution wouldn't have made any sense.
Therefore, we don't need any help to understand that the only possible root for the radius is 20. So,
Condition 1 is enough - answer A.
Attachments
File comment: The updates drawing with solution.

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