A client plans to retire in 15 years and will need to withdraw $50,000 from his retirement account each year for 10 years, beginning on the day he retires. After that, he will need to withdraw $20,000 per year for 25 years. The account returns 4% annually. The amount he needs to have in the account on the day he retires is closest to:

We can treat these cash flows as a 35-year annuity due of $20,000 per year plus a 10-year annuity due of an additional $30,000 per year. With calculator in BGN mode:
$20,000 per year for 35 years: N = 35> PMT = 20,000, I/Y = 4, FV = 0; CPT PV = -388,224
$30,000 per year for 10 years: N = 10, PMT = 30,000, I/Y = 4, FV = 0; CPT PV = -253,060
Total: $641,284