CFA Vol.2 EOC Q.13 B i. Time Horizon

Answer Key says two stage but would it not be 3 stages due to: 1. 18 years; from now to retirement 2. Children education in retirement and 3. Retirement passed Children education or because we are considering the 2 Mill needed in 18 years for both then we consider both education and retirement as one time horizon? Thanks NVC

Compare this with Q 11 where daughter goes to college for 4 years. They considered three stages. The CFAI text says changing CF and resource circumtances decide the end of stage and begining of new stage . In Q 11 CF does change since college expenses are 40000 they will be reduced after 5 years In Q 13 there is no talk of ongoing expenses for college that will end sometime in retirement hence only two stages for Q13