What would be the most convincing way to demonstrate that the replacement stream in Example 8.6A is economically equivalent to the given stream?

Example 8.6A:

Payments of $2000 and $1000 were originally scheduled to be paid one year and five years, respectively, from today. They are to be replaced by a $1500 payment due four years from today, and another payment due two years from today. The replacement stream must be economically equivalent to the scheduled stream. What is the unknown payment, if money can earn 7% compounded semiannually?