Scheduled payments of $800 due two years ago and $1000 due in five years are to be

Question:

Scheduled payments of $800 due two years ago and $1000 due in five years are to be replaced by two equal payments. The first replacement payment is due in four years and the second payment is due in eight years. Determine the size of the two replacement payments if interest is 12% compounded semi-annually and the focal date is four years from now.