Let's say I save $400 per month for 20 years, and my investment grows at 6% the whole time that I'm saving. How much money will I have at the end of 20 years?

Now let's say the 20 years have gone by and now instead of saving money, I'm living off my savings by withdrawing an annual lump sum of $25,000. Let's also say any money I haven't withdrawn continues to earn interest, but now it's only growing at 3% per year because I decided to move into less risky investments since I can't afford to risk my nest egg anymore. How many years can I live on this investment before I'll run out of money?