I need help with the following practice problem. I think I need to work backwards, but I am not sure how to get started even.

Charles Howard just discovered a one-time use, two-way time portal in the back room of a gas station. He can use the portal to travel to the time: Jan 1, 1936, stay for the day, and then return to Jan 1, 2021. Charles wants to cash in on his discovery by depositing money into a bank account while in 1936. When he returns to 2021, Charles wishes to:

Purchase a mansion for 19 million dollars immediately.

Maintain a luxury lifestyle, which Charles estimates will cost $2 million per year for the next 40 years.

Purchase a professional sports team in 2025 for an estimated cost of $45 million.

Donate $50 million to his favorite college on Jan 1, 2051.

If Charles can earn 13% percent per year (simple annual rate), how much does Charles need to deposit on Jan 1, 1936 in order to be able to pay for his planned future expenditures?