A fund earning 4% effective has a balance of $1,500 at the beginning of the year. If $100 is added to the fund at the end of three months and if $700 is withdrawn from the fund at the end of nine months, find the ending balance under the assumption

a(1)/a(t) = 1 + ( 1 - t )i

help i have this finance assignment due....and the answer i got does not seem to be right at all...can someone help me thanks