Slopes of Perpendicular Lines

The line y = (3/5)x - 4 has been rotated 90 degrees counterclockwise. What is the slope of line C'A'?

Could you rotate the line y = (3/5)x - 4, 90 degrees clockwise? If so, what is the slope of line A'C'?

The original line (AC) and the rotated lines (A'C') are perpendicular because they form a 90 degree angle where they intersect. Do you notice a relationship between their slopes?