Please explain it

The figure below shows the level curves of the function ax, y) The tangent plane approximation to f at the point P(x0, go) is written as T(m, y) = c -l- m(x x0) + n(y yo).What are the signs of c, m, and n? .c>0,m0 Oc0,m>0,n>0 Oc0,n