The text mentions "perpetuities" as though they're normal financial arrangements which simply generally exist. But "forever" is a long time, so there's only one application where this really fits: stock. There's an entire chapter on stock later on, so I won't cover that now. I'll simply just jump to the math. What's the value today of an investment which will pay you $3.12 every quarter, (that is, every 3 months), forever, if the "interest rate" to use is 10.5% APR? Hint: Does it make any difference to the answer if you define "forever" as 300 quarters versus 600 quarters or more