Solution: The Lorentz system is

dx/dt=s(y-x)

dy/dt=r*x-y-z*x

dz/dt=x*y-b*z

let s,r and b are positive

assume s=10

r=28

b=8/3

if r>1 then two additional critical point appear

(±vb(r-1),±vb(r-1),r-1)

=(±v8/2(28-1),±v8/2(28-1),28-1)

=(±8.48,±8.48,27)

this pair of equilibrium points are stable only if r<s(s+b+3/s-b-1)

if r<1 then there is only one equilibrium point which is at the origin,this point corresponds to no conversion.