Explanation:

The SVG image is built from three filled polygon faces, one white ellipse, and two white diagonal line segments. The three < polygon > elements define the black cube faces by connecting multiple coordinate points. The small white oval on the top face must be an < ellipse > because the markup uses cx, cy, rx, and ry; these attributes define an ellipse center point and horizontal/vertical radii. The diagonal marks on the left and right faces are straight segments, so they must use the SVG < line > element. A line is defined with starting coordinates x1, y1 and ending coordinates x2, y2. The first diagonal runs from the bottom point (200,365) to the upper-left point (50,100). The second diagonal must mirror it on the right side, so it starts at (200,365) and ends at (350,100). Therefore, the final coordinate selection is x2= " 350 " y2= " 100 " . References/topics:
SVG shapes, < polygon > , < ellipse > , < line > , coordinate-based vector drawing, SVG markup construction.