The answer is:
The third and fourth inequalities become 
and 
.
The feasible solution set consists of the cross-hatched region lying within the first quadrant.
The origin is a vertex.
The y-intercept of Y1 is a vertex (use CALC value).
The intersection of Y1 and Y2 is a vertex (use CALC intersect).
The x-intercept of Y2 is a vertex (use CALC zero).
If you missed this question, you should review this skill.