this is one question with multiple parts

Q3.1 5 Points Threads are lighter than processes. Why? Q3.2 Amdahl's law 6 Points Suppose an application has 70% serial and 30% parallel operations. If the application runs on a 4-core machine, how much speedup, at best, can it get compared to running on a 2-core machine? Q3.3 5 Points What is the problem of the one-to-one model of user-level threads and kernel-level threads mapping? How does the two-level model eliminate this? Q3.4 4 Points How does the pthread_join() call in threads differ from its wait counterpart in processes