Commands to generate graphics for Statement of Problem.

Input := 

Plot[(1+Sign[x-100])/2,{x,0,200},PlotStyle->Thickness[.015],
AxesLabel->{"Mass of Rock",
		"% saying mass > 100 g"}]

Output =

-Graphics-

Input := 

Plot[.5,{x,0,200},PlotStyle->Thickness[.015],PlotRange->{0,1},
AxesLabel->{"Mass of Rock",
		"% saying mass > 100 g"}]

Output =

-Graphics-

Input := 

data = {{10,.02},{40,.1},{70,.21},{90,.45},{100,.5},
        {120,.65},{125,.75},{150,.9},{175,.98}};

Input := 

ListPlot[data,PlotStyle->{PointSize[.02]},
		PlotRange->{{0,200},{0,1}},
			AxesLabel->{"Mass of Rock",
		"% saying mass > 100 g"}]
			

Output =

-Graphics-