ClearAll;
$DefaultFont = {"Times-Roman",10};
Needs["Graphics`Graphics`"];
a = 24; b = 33.4;
maize = {{12,0}, {15,9}, {20,20}, {25,29}, 
		 {30,35}, {35,38}, {45,30}, {50,7}, {51,0}};
m0[t_]:= t(t-12)(51-t)(1884 - 71 t + t^2);
approxm[t_] = Fit[maize,{m0[t]},t];
s = Abs[FindMinimum[-approxm[t],{t,37,37.1}][[1]]];
appm[t_] = approxm[t]/s;
tang = D[appm[t],t]/.t->a;
chor = (appm[b] - appm[a])/(b-a);
xl = a - appm[a]/tang;
xh = a + (1.05 - appm[a])/tang;
xl2 = a - appm[a]/chor;
xh2 = a + (1.05 - appm[a])/chor;
line1 = Graphics[{Dashing[{0.01,0.01}],
				  Line[{{xl,0},{xh,1.05}}]}];
line2 = Graphics[{Thickness[0.0008],
				  Line[{{a,appm[a]},{b,appm[a]}}]}];
line3 = Graphics[{Thickness[0.0008],
				  Line[{{b,appm[a]},{b,appm[b]}}]}];
line4 = Graphics[{Dashing[{0.01,0.01}],
				  Line[{{a,0},{a,appm[a]}}]}];
circ = Graphics[Circle[{xl,0},{5,0.2},{0,0.75}]];
text = Graphics[{Text[FontForm["q",{"Symbol",9}],{xl+3,0.05}],
				 Text[FontForm["M",{"Times-Roman",10}],{a+2,0.05}],
				 Text[FontForm["O",{"Times-Roman",10}],{xl-1,0.05}],
				 Text[FontForm["P",{"Times-Roman",10}],{a-1,appm[a]+0.05}],
				 Text[FontForm["R",{"Times-Roman",10}],{b+2,appm[a]}],
				 Text[FontForm["Q",{"Times-Roman",10}],{b,appm[b]+0.05}],
				 Text[FontForm["x +   x",{"Times-Roman",10}],{b,-0.035}],
				 Text[FontForm["x",{"Times-Roman",10}],{a,-0.035}],
				 Text[FontForm[d,{"Symbol",9}],{b + 0.6,-0.031}],
				 Text[FontForm["y +   y",{"Times-Roman",10}],{-1.5,appm[b]}],
				 Text[FontForm[d,{"Symbol",9}],{-0.9,appm[b]+0.005}]}];
plot = Plot[appm[t],{t,15,43},
			PlotLabel -> "Figure 30.6\n\n   y = F(x)",
			Ticks->{{{b," "}},
			{{appm[a],"y"},{appm[b]," "}}},
			PlotRange->{{-3,52},{-0.1,1.05}}];
Show[plot, line1, line2, line3, line4, circ,text]