Propose a suitable mechanism for the formation of the mixed anhydride in the reaction indicated below:
C6H5CH2CO2H + (CF3CO)2O yields C6H5CH2C-O-CCF3 (also has an O double bonded to the third C with two single pairs of electrons on the O. the same is double bonded to the fourth C. the middle O also have two lone electron pairs) + CF3CO2H