The estimate on my new project was done by another project manager and is hopelessly unrealistic, but approved. What can I do?

A. Rebaseline. Do the project with the new estimates you feel are correct.

B. Change the estimate and circulate word that the old project manager is incompetent.

C. Document your findings and present the stakeholders with options.

D. Do nothing. To have an estimate is what counts. No one expects you to actually work within it.