A: For the Dentist, their average income in 30 years is $4,282,200
B: For the Manager, their average income in 30 years is $2,592,000
C: The difference in both their earnings is $1,690,200
Work: So, I just multiplied their average earnings by 30, and that's what their average income will be in 30 years. For the difference, I subtracted the higher earning by the lower earning, and that's the difference.
I hope this helps you. :)