## Thomas' Calculus 13th Edition

a. Domain : The set of all $(x,y)$ corresponding to $x^2+y^2 \lt 16$ . b. Range: $z\geq \dfrac{1}{4}$ c. Level Curves: The level curves are the circles whose center is at (0,0) with radius $r \lt 4$ d. Boundary point lies at the circle $x^2+y^2=9$ e. Open only f. Bounded