How to solve for subsystem in mixed finite element spaces

1

I am new in FeniCS and working in mixed finite element space M containing 5 subspaces.
RT1 = FiniteElement(“RT”, mesh.ufl_cell(), 1)
CG1 = FiniteElement(“CG”, mesh.ufl_cell(), 1)
RT2 = FiniteElement(“RT”, mesh.ufl_cell(), 1)
M = Mixed Element([RT1, CG1, RT1, RT1, CG1])
Sol = Function(M)
(a, b, c, d, e) = split(Sol)
The unknowns X = (a,b,c) are obtained from system of equations
M_1 X = L1 …(1)
Then, X is used to evaluate Y = (d,e) via
M_2 Y = L2 …(2)
How can I modify solve kind of commands for X and Y.

solve(M_1, Sol.vector([0:2]), L1)
and solve(M_2, Sol.vector([3:4]), L2 ) not working

2

If you want to solve the systems individually, you should not use Mixed elements.

You should make one Mixed FunctionSpace for 0-2 and one for 3-4.

For clarity, please state the set of PDEs you are trying to solve (in maths).

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