The very first probability exercise, should be easy

Hi,

I just began a probability course and I am already in problems. This should be extremely easy for anyone ever done these, but I'm just lost with these notations. So I'm first and foremost looking to understand that what the actual question is, not so much of the answer (because I'm sure once I get the idea I'll be able to solve these by myself).

So here's the exercise:

Perform the following set operation:

http://koti.kapsi.fi/~jflurrie/Koulu/1b.JPG

What am I supposed to do with it? k goes from 1 to infinity, making the first part of the comparison one, half, third, quarter etc. and the last part of comparison is 3, 3½, 3.67, 3.75... but what else I'm supposed to do? What kind (what form) of answer I should get? Since this is union, is the answer a 2d-area where lower left corner (so minimum of x and y) is almost in 0,0 and upper right corner (maximum of x and y) is almost in 4,4?

So step-by-step, what am I supposed to do with this exercise?

Thanks for anyone even trying to help!