Define both of the two types of risk assessments, and their purposes/use cases. Perform one type of risk assessment based on the scenario given below, while using both reasonably estimated and calculated numerical values as applicable.

Justify your response to the scenario's prompts with a detailed explanation or reasoning of each aspect, and show the calculations in detail.

The scenario is:

You work for a large company with many employees. Every month, about a half-dozen employees fall victim to an executive impersonation scam and each ends up buying a $200 iTunes gift card that gets sent to the scammers. What do you estimate to be the total losses for a year due to this scam via a risk assessment? Explain your reasoning.