Exchange user's inherited rights

Hi,

We have Exchange 2010 and I've created two useful script for my scenarious:

1) Get-Mailbox -ResultSize Unlimited | Get-AdPermission | ?{($_.user -like "*user*") -and ($_.IsInherited -eq $false)} | select Identity, ExtendedRights, User | ft –wrap
That script shows me AD level (SendAs) for my selected user account and on which other users that selected user has rights, and which level of rights.

2) Get-Mailbox -ResultSize Unlimited | Get-mailboxPermission | ?{($_.user -like "*user*") -and ($_.IsInherited -eq $false)} | select Identity, AccessRights, User | ft –wrap
That script shows me which other mailboxes could be opened by selected users.

Now, I need two more scripts.

a) similar like to 1), but show on opposite way - select target user account and show which other users has SendAs rights and which level

b) similar like to 2), but show on opposite way - select target user account and show which other users can open his/her mailbox?

Can you please advise how to prepare these scripts?

Thank you in advance!