Answer: Some part of the question is missing. I can not see what investment plan A and B are.
Step-by-step explanation:
To understand annuity, think like you are saving same amount of money in bank after same period of time. Like, saving $100 every month. There are 2 types of annuity; ordinary annuity and annuity due. In the example given by me, ordinary annuity would be saving the money at the end of each month and annuity due would be saving the money at the start of each month. The payments are supposed to be equal at start or end of the consecutive period over a pre-defined length of time. Frequency of payments can be monthly, quarterly, semi annually or yearly.