<em>CA </em>⁻¹ is undefined because there are more columns in <em>A </em>⁻¹ than there are rows in <em>C</em>.
We have been given a diagram and we need to find the value of arc angle a.
According to one of the circle theorems the angle at the centre of a circle is twice the angle at the circumference subtended by the same arc.
Therefore, arc angle a will be twice of the angle at circumference, that is, 34 degrees.
Therefore, value of angle a is:

B.
The line starts at the origin and goes down by two.