Neucleophilic Acyl substitution of unsymmetrical Acid Anhydrides

sodaboy7

Consider the following reaction:

RCOO-COR + R'-OH → RCOO-R' + RCOOH (where -R is an alkyl group)

In above reaction the acid anhydride and an alcohol forms ester and carboxylic acid.
The acid anhydride used in this case is a symmetrical on that is containing only one alkyl group (R). My question is that if it is unsymmetrical (say R₁COO-COR₂), which alkyl group will form ester and which alkyl group will form carboxylic acid. That is will ester formed will have R₁ or R₂ ?