angles formed by chords

[needzmathhelp]

I've been given the following diagram and told to find x, y, z, and the measure of arc CD. O is the center of the circle.

I know y=60 because arc AB is 120? and an inscribed angle is half the measure of its intercepted arc. I need to find x (m?B), z (measure of arc BC), and the measure of arc CD.

 

[Denis]

I know y=60 but that's it.

HOW do you know that? Is it a given? 60 degrees?
Is arc AB = 120? What does z represent?

Please post original problem IN FULL.