The ornamental design for a seat and back rest for a chair, as shown and described.
FIG. 1 is a perspective view showing the top, left side and front of a seat and back rest for a chair which forms my new design, the broken lines in this and other figures showing other parts of the chair being for illustrative purposes only and forming no part of my design;
FIG. 2 is a slightly enlarged left side elevational view thereof;
FIG. 3 is a slightly enlarged right side elevational view thereof;
FIG. 4 is a slightly enlarged top plan view thereof; and,
FIG. 5 is a slightly enlarged front elevational view thereof.
The short, broken lines on the chair in FIGS. 1–5 are understood to represent stitching.