description: mbr(ket, sp) returns the coeff of 'ket' in 'sp'. If 'ket' not in 'sp' then return |> examples: mbr(|b>, |a> + |b> + |c>) |b> mbr(|c>, 0.3|a> + 2|b> + 9.7|c> + 13|d>) 9.7|c> mbr(|x>, 0.3|a> + 2|b> + 9.7|c> + 13|d>) |> see also: is-mbr, intersection