help pls multivariable calculus

Hello friends! I'm doing my homework but I'm having problems with two exercises :c help

 

1. solve

\(\iint_R \frac{1}{4-3x^2-y^2} \,dx\,dy, where\ R=\{(x,y)|3x^2+y^2\leq 1\}\)

 

 

2. Determine the center of mass of the homogeneous bodies limited by the indicated surface:

\(2z=x^2+y^2,x^2+y^2+z^2=3,z \geq 0\)

 

 

thanks a lot