The radius of the circumscribed circle is 6.5 cm.
The measure of angle OAC is 67.4°.
Since AB is represents the diameter of the given circle centered at O, we can reasonably infer and logically deduce that inscribed angle C must be a right angle with a measure of 90 degrees.
In order to determine the length of diameter AB, we would have to apply Pythagorean's theorem as follows;

AB = 13 cm.
In Mathematics, the radius of a circle is half the length of the diameter;
OA = AB/2
OA = 13/2
OA = 6.5 cm.
Based on the diagram, the measure of inscribed angle B is one-half the measure of arc AC;
m∠B = 45.2°/2
m∠B = 22.6°
Now, we can determine measure of angle OAC by using the complementary angles property;
m∠B + m∠OAC = 90°
m∠OAC = 90° - 22.6°
m∠OAC = 67.4°.
Complete Question:
Suppose AC = 5 cm, BC = 12 cm, and mAC = 45.2°.
To the nearest tenth of a unit, the radius of the circumscribed circle
is __?__ cm and m∠OAC = __?__°.