not able to upgrade

[Sirisha Peram]

Could not calculate the upgrade

An unresolvable problem occurred while calculating the upgrade.

 This can be caused by:
 * Upgrading to a pre-release version of Ubuntu
 * Running the current pre-release version of Ubuntu
 * Unofficial software packages not provided by Ubuntu

If none of this applies, then please report this bug using the command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal.

How to resolve this?

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: ubuntu-release-upgrader-core (not installed)
ProcVersionSignature: Ubuntu 3.2.0-23.36-generic 3.2.14
Uname: Linux 3.2.0-23-generic i686
ApportVersion: 2.0.1-0ubuntu5
Architecture: i386
Date: Wed Mar 1 17:48:24 2017
InstallationMedia: Ubuntu 11.04 "Natty Narwhal" - Release i386 (20110427.1)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to precise on 2017-03-01 (0 days ago)

[Brian Murray (brian-murray)]

Thanks for taking the time to report this bug and helping to make Ubuntu better. Could you please add the log files from '/var/log/dist-upgrade/' to this bug report as separate attachments? Thanks in advance.

[Launchpad Janitor (janitor)]

[Expired for update-manager (Ubuntu) because there has been no activity for 60 days.]