How do I graph inequalities

-- Get the inequality into the form with 'y' on one side and everything else on the other side.

-- Graph it as if it were an equation.  That gives you a line.

-- If the inequality is " y less than... ", then the graph of the inequality is all of the infinite plane under the line, but not the line itself.

-- "y less than or equal to ..." . . . . . the line and all of the area under it
 
-- "y greater than ... " . . . . . all of the infinite plane above the line, but not the line itself.

-- "y greater than or equal to ..." . . . . .  the line and all of the area above it.

The density of the cube is 40