I am new to excel. Trying to set up a formula for the following 2 examples

1. Semi Annual payments of $440,000 for 20 years, or 8Million dollars now,
what is the interest rate that was used to arrive at the 8 million dollars

2. Semi annual payments of $440,000 for 20 years, an interest rate of 7%,
how much should the payment be in a lump sum today?

Thank you for your help, if you could provide me the formula so that I can
play around with various amounts or interest rates that would be helpful.