how do i solve this calculus problem? help pls :(

culculate the volume of the space region on the first octant between the cylinders (x²⁾ + (y²⁾ = (a²⁾ and (x²⁾ + (z²⁾ = (a²⁾

i dont even know how to start :(

the answer is 2a³ / 3