6. For your valiant services in the latest conflict against the Persians, the Babylonian king Belshazzar offers you the rich sum of 100 shekels each year for the next twenty years. (A typical year of manual labor was worth about 10 shekels). The thing is, you don't expect to live very long in ancient Babylon and so the going interest rate is 25 percent. What is this stream of benefits worth to you today