$3.$ Answer the following questions $(25$ points$)$: a$)$ What kind of tasks $($concurrent programs$)$ do not require any kind of synchronization? Use an example to explain. b$)$ What Java program unit can run concurrently with the main method in an application program. c$)$ A Producer and a Consumer share a buffer. DEPOSIT saves a value to the buffer and FETCH takes a value from the buffer. Two semaphores spotunmarked and spotcalculate are used for cooperation synchronization. Read the following code, then describe the actions of the release operation for the semaphore step by step $($do not copy the code$).$ semaphore spotcalculate $,$ spotunmarked ; spotcalculate.count $=0$ ; spotunmarked.count $=$ BUFLEN ; Task Producer; loop $-$ produce VALUE $-$ wait $($ spotunmarked $)$ ; DEPOSIT $($ VALUE $)$ ; release $($ spotcalculate $)$ ; end loop ; endProducer ;