HowTo:upper and lowerlimit of integral from Cartesian coordinate to polar coordinate?

I'm stuck in finding integration of a integral. I'm given a integral and asked to change the Cartesian

integral into an equivalent polar integral and then evaluate the resulting integral.

The integral is:

So i replaced with .

The book says:

But how do you find the upper and lower boundary of and in polar coordinate from Cartesian coordinate?

The book I'm following is vague about the procedure.

There must be a way to find it. But can't seem to figure it out.

Can anyone kindly explain the method?