[t,x]=ode45('shark1',[0 15],[25 2]);
plot(t,x(:,2)./(x(:,2)+x(:,1)),'r')
hold on
[t,x]=ode45('shark2',[0 15],[25 2]);
plot(t,x(:,2)./(x(:,2)+x(:,1)),'g')
hold on
t=0:1:9;
x=0.01*[11.9 21.4 22.1 21.2 36.4 27.3 16 15.9 14.8 19.7];
plot(t,x,'g')
