What are some of the issues discussed in Module 3 that specifically make legacy system migration difficult? Choose all that make it difficult. a. Legacy systems may use non-cutting-edge technologies b. Adding more people to a project usually makes it go slower c. Separating out the important parts in a legacy system is difficult due to "tangled code" d. Those who architected and designed the system are usually long gone from the company e. Business stakeholders usually demand that all existing functionality must be replicated in a replacement system