Which is more accurate SARS-CoV + MERS-CoV = SARS-CoV2 or SARS-CoV + MERS-CoV = MERS-CoV2?

Abstract

The functions of existing proteins are explained based on the proteins of previously known coronaviruses. While the role of most non-structural proteins in viral replication has been defined, the role of some is still not fully explained. Four structural proteins have an essential role in combining virion and being a target for coronavirus infection pathogenesis and drug development.