Puneet,
The HR plan is an input to Estimate Costs because the PM will need to understand the fixed cost of labor associated with the project. For example, workers will need to be paid, they may have certain benefits that will need to be paid such as leave, medical, etc, they need costly rewards, and they may require training. The resource calendar is an input to Determine Budget because it includes how the costs will be applied over time (i.e. the time-phased project budget) while Estimate Costs does not necessarily include a comprehensive analysis of the impact of time.
- Steven