Derek receives a perpetuity. It has annual payments with the first payment in exactly eight years. The first payment is $$10,000,$ the secont payment is $$15,000,$ and then the payments alternate between $$10,000$ and $$15,000$ until there have been a total of thirty payments. After that, the payments are all $$10,000.$ Find the present value of this perpetuity if the effective interest rate is $4\%.$