<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def preScale(self, sx, sy):
 """Calculate pre scaling and replace current matrix."""

        self.a *= sx
        self.b *= sx
        self.c *= sy
        self.d *= sy
        return self