Use the Limit Definition of the Partial Derivative to Compute $\text { Find } \frac { \partial f } { \partial z } \text { at the point } ( 6 , - 5,5 ) : f ( x , y , z ) = x y z - 10 y ^ { 2 } - 7 z$

Use the limit definition of the partial derivative to compute the indicated partial derivative of the function at the specified point.
- $\text { Find } \frac { \partial f } { \partial z } \text { at the point } ( 6 , - 5,5 ) : f ( x , y , z ) = x y z - 10 y ^ { 2 } - 7 z$