Hello, boys , help "blonde" solve two problems on the double, triple and surface integrals, please.

#1. Find the center's coordinates of the gravity of a homogeneous surface:

#2. Calculate the surface integral of the first kind of surface ,

where - part of the plane , which cut coordinates planes.

How should I start to solve these problems? Do I need to change the coordinates in the first problem?

Which a figure is a projection on the plane XOY?