Use the tangent-chord theorem:
The included chord-tangent angle is half the size of the intercepted arc.
The intercepted arc is "c".
The included chord-tangent-angle is the supplement of 110=70 degrees.
Therefore from the tangent-chord theorem, 70 degrees = half the size of arc "c"
=>
arc "c" = 2*intercepted angle = 2*70 degrees = 140 degrees.
