The time required to complete a project is normally distributed with a mean of $80$ weeks and a standard deviation of $10$ weeks. The construction company must pay a penalty if the project is not finished by the due date in the contract. If a construction company bidding on this contract wishes to be $90$ percent sure of finishing by the due date, what due date $($project week #$)$ should be negotiated? a$.81\mathrm{.}28$ b$.81\mathrm{.}82$ c$.92\mathrm{.}80$ d$.0\mathrm{.}81954$