My study is to measure the synergy between ICT and knowledge Management in Tourism industry (Particularly, tour operating sector) from the employees persoective.

I have a finite list of firms and the number of employees working with each firm and they are as follows:

City A- 46 firms-416 employees

City B-32 firms-357 employees

City C-22 firms- 395 employees

City D- 11 firms-214 employees

I am planning to adopt a stratified proportional random sampling method. As my population is around 1,382 employees, how many responses should I take for my study?