$ have type PB0. Then we set $$\begin{aligned}   & b'(0)  :=  0 , \quad  b'(0) := 0 , \quad  b'(0) := b(0) + c(0)  , \\    &  b'(00)  := b(00) + c(00)  , \quad  b'(00) := 0 , \quad  b'(00) := 0 .\end{aligned}$$ No