import graph;
size(9cm,9cm,IgnoreAspect);

real t0 = 2007.5;
real[] year = {	2007.75,2008.75,2009.25,2009.9};
real[] price= {	18,	22,	24,	26};

real approx(real x){return 3.75982*x-7530.64;}

for(int i=0;i<4;++i)
	dot((year[i],price[i]),2mm+red);

draw(graph(approx,t0,2010),blue);

xaxis(BottomTop, RightTicks(Step=1,step=0.5,extend=true,ptick=lightgrey));
yaxis(LeftRight, RightTicks(Step=4,step=2,extend=true,ptick=lightgrey));
xequals(t0, ymax=27, p=linewidth(1.5pt), Arrow(2mm));
yequals(approx(t0), xmax=2010.25, p=linewidth(1.5pt), Arrow(2mm));

label(rotate(aTan(1.1))*"$y=3.76\,x-7531$",(2009,22),blue);