function g = prob613fun(x,y)
y1 = x(1);
y2 = x(2);
y3 = x(3);
y4 = x(4);
y5 = x(5);
y6 = x(6);
y = [x(1) x(2) x(3) x(4) x(5) x(6)];
ca0 = 1.5;
tau = 5;
cb0=2;
kd1 = 0.25;
ke2 = 0.1;
kf3 = 5;
re = ke2*y1*y4;
rf = kf3*y2*y3^2;
ra = -kd1*y1*y2^2-3*ke2*y1*y4;
rb = -2*kd1*y1*y2^2-kf3*y2*y3^2;
rc = kd1*y1*y2^2 + ke2*y1*y4-2*kf3*y2*y3^2;
rd = kd1*y1*y2^2 -2*ke2*y1*y4+kf3*y2*y3^2;
f1 = y1-ca0-ra*tau;
f2 = y2-cb0-rb*tau;
f3 = rc*tau - y3;
f4 = rd*tau - y4;
f5 = re*tau - y5;
f6 = rf*tau - y6;
g = [f1 f2 f3 f4 f5 f6];
