Find and classify any equilibrium points in the Romeo and Juliet problem for the following cases. Solve the systems and describe their affections as a function of time.

a. \(a=0, b=2, c=-1, d=0, R(0)=1, J(0)=1\).

b. \(a=0, b=2, c=1, d=0, R(0)=1, J(0)=1\).

c. \(a=-1, b=2, c=-1, d=0, R(0)=1, J(0)=1\).