With the proposed architecture/config there is no way for R1 to reach 126.96.36.199 on AS54. Is it a bug on the workbook? Thanks.
Yep 112.x.x.x is ok (it belongs to R9) but if you try to reach 28.x.x.x which is also in AS 54 but in R10, it will not work. Actually it will form a loop between R1->EIGRP domain ->R3 -> R1. This behaviour is because the EIGRP domain will send this traffic always to R3, the only router where BGP to EIGRP redistribution is in place, because R3 is the source of the prefix distribution at the EIGRP domain.