Find the Domain and Range and Describe the Level Curves $x y$

Multiple Choice

Find the domain and range and describe the level curves for the function f(x,y) .
-f(x, y) = -6x + 8y

A) Domain: all points in the $x y$ -plane; range: real numbers $z \geq 0$ ; level curves: lines $- 6 x + 8 y = c , c \leq 0$
B) Domain: all points in the $x y$ -plane; range: all real numbers; level curves: lines $- 6 x + 8 y = c$
C) Domain: all points in the $x y$ -plane; range: all real numbers; level curves: lines $- 6 x + 8 y = c , c > 0$
D) Domain: all points in the $x y$ -plane; range: real numbers $z \geq 0$ ; level curves: lines $- 6 x + 8 y = c , c \geq 0$