On January 1,1988, Antonio invests $9 , 400 in an investment fund. On January 1,1989 his balance is $10 , 700 and he deposits $2 , 300 . On July 1,1989 his balance is $14 , 100 and he withdraws $1000 . On January 1,1992 his balance is $ P . Express his annual time-weighted yield ( i tw ) as a function of P . i tw =.