Find the Domain and Range and Describe the Level Curves $\le$

Find the domain and range and describe the level curves for the function f(x,y) .
-f(x, y) = 4x + 3y

A) Domain: all points in the xy-plane; range: all real numbers; level curves: lines 4x + 3y = c, c > 0
B) Domain: all points in the xy-plane; range: all real numbers; level curves: lines 4x + 3y = c
C) Domain: all points in the xy-plane; range: real numbers z $\le$ 0; level curves: lines 4x + 3y = c, c $\le$ 0
D) Domain: all points in the xy-plane; range: real numbers z $\le$ 0 ; level curves: lines 4x + 3y = c, c $\le$ 0