You have just had your 30th birthday. you have two children. one will go to college 10 years from now and require four beginning-of-year payments for college expenses of $10,000, $11,000, $12,000, and $13,000. the second child will go to college 15 years from now and require four beginning-of-year payments for college expenses of $15,000, $16,000, $17,000, and $18,000. in addition, you plan to retire in 30 years. you want to be able to withdraw $50,000 per year (at the end of each year) from an account throughout your retirement. you expect to live 20 years beyond retirement. the first withdrawal will occur on your 61st birthday. what equal, annual, end-of-year amount must you save for each of the next 30 years to meet these goals, if all savings earn a 13 percent annual rate of return?