Find a Function with the Given Partial Derivatives $\frac { \partial f } { \partial x } = y \cos ( x y )$

Multiple Choice

Find a function with the given partial derivatives $\frac { \partial f } { \partial x } = y \cos ( x y )$ and $\frac { \partial f } { \partial y } = x \cos ( x y )$

A) $f ( x , y ) = \cos ( x y )$
B) $f ( x , y ) = \sin ( x y )$
C) $f ( x , y ) = - \sin ( x y )$
D) $f ( x , y ) = - \cos ( x y )$