Can a job worker engaged in manufacturing

hi

a company works as a job worker but was outside the purview of excise before budget, but post budget the process of conversion (coal into coke) carried out in the premises of job worker tantamounts to manufacture.

suppose the company act both as job worker for two clients as well as manufacturer and the conversion process is carried out alltogether as it is not possible to carry the conversion process separately for each of the clients. now the output is based on the quantity of input as per accepted valuations. any extra production will lead to surplus and will be sold in the open market by the job worker.

now my question is

whether it is possible to carry out the conversion process together for the job work(for both clients) & his own manufacture

applicability of central excise

admissibility of cenvat credit on inputs used my job worker for conversion

regards

nihit dalmia