Nineteen-year-old Spanish tennis sensation, Carlos Alcaraz, beat 23- year-old Norwegian Casper Ruud in 4 sets to win the 2022 US Open, collecting a prize of $2.6 million, bringing his total year to date winnings in 2022 to $7.4 million.  

a ) If Carlos decided to invest half of his US Open winnings, plus $ 250,000 from his future quarterly earnings ( starting next quarter) into an investment earning 5.25 % compounded quarterly for the next 10 years, how much would he have at the end of 10 years.  

b ) If Carlos uses the accumulated funds from (a) to donate to his favourite charities, how much could he donate annually at the end of each year, if he wanted to continue his donations for 20 years?