Alice's company implements simple Role-Based Access Control. There are two roles, R1 and R2, and there are three objects O1,O2 and O3. The set of operations are {r (read), w (write), x (execute) } - The set of permissions is {(O1,r),(O1,x),(O2,r),(O2,w),(O2,x),(O3,x)}. - The set of permission-role assignments relation is {((O1,r),R2),((O1,x),R2),((O2,r),R1),((O2,w),R1),((O2,x),R2),((O3,x),R1)}. Bob is assigned to role R2. Pick all the requests he can be granted. Read O1. Read O2. Modify O1. Execute O3. Execute O1. Read O3. Execute O2. Modify O2