mbr(ket) sp returns the coeff of ket in the given superposition if ket is not in the sp then the returned coeff is 0
mbr(|b>) (|a> + |b> + |c>) |b> mbr(|c>) (0.3|a> + 2|b> + 9.7|c> + 13|d>) 9.700000|c> mbr(|x>) (0.3|a> + 2|b> + 9.7|c> + 13|d>) 0|x>