function dy=lotka(t,y);

x=100000;
c1=.0002;
c2=.01;
c3=10;

y1=y(1);
y2=y(2);
dy1=c1*x*y1-c2*y1*y2;
dy2=c2*y1*y2-c3*y2;

dy=[dy1;dy2];