Answer
$m\widehat{TCB}=270^{\circ}$
Work Step by Step
We must know that the measure of a minor arc is equal to the measure of its corresponding central angle.
In the given question, we can see that the related minor arc of major $\widehat{TCB}$ is $\widehat{TB}$ .
This implies that
We have $m\widehat{TB}=m\angle TPB=90^{\circ}$. This implies that $m\widehat{TCB}=360^{\circ}-90^{\circ}$
or, $m\widehat{TCB}=270^{\circ}$
