eBGDAElet ring1=10502221244202020P. M.let ring30222122(1)402020let ring50232123(1)602221P. M.let ring72121012(0)8021209022212P. M.let ring1002020110222122(1)1202020let ring130232123(1)140222115021201220let ring1612202220170232123(1)18=6002221let ringlet ring1922203202002212