We need to find the reflection of point P across the line y = 1.
Reflection across the line y = k transforms the point (x,y) into (x, 2k - y).
Applying this rule to the point P(-2, 4) with the line y = 1 (k = 1), we get:
P(-2, 4) → (-2, 2x1 - 4) → P'(-2, -2)