Jenny decides to save for her retirement starting on her 25th birthday. She puts $1,000 a year in an investment that earns 10% a year compounded annually. She does this for 20 years (she is then 45, and has invested $20,000) and then stops adding more money. She then leaves the money invested at 10% annually until she is 65, when she retires. Peter, Jenny's twin brother, does not save for his retirement until his 45th birthday, and then he starts investing a fixed amount each year at 10% per annum for 20 years (at which time both Peter and Jenny are 65)

How much does Peter have to invest per year to have the same amount of money as Jenny when she retires?