can you answer 12a and 12b plese

Given the access matrix below, answer questions (i-iii). i. Can a process in domain D_1, grant read privileges for object F_ to a process in domain D_2? Why or why not? ii. Can a process in domain D_ revoke the write privileges of a process in domain D_1 for object F_ ? Why or why not? iii. Can a process in domain D_2 give read, write, and execute privileges for object F_2 to a process in domain D_3? Why or why not? b. Two professors are discussing the security of a distributed system in which the key used to encrypt messages is known. Professor A claims that knowing the encryption key will allow him to decrypt any message sent between nodes in the system once he determines the type of cryptography used, thus making the system insecure. Professor B claims it is possible for the system to be secure, depending on what method is used to encrypt messages. Which professor is right, and why