LOAN AGREEMENT by and among KBSIII 60 SOUTH SIXTH STREET, LLC, KBSIII PRESTON COMMONS, LLC, KBSIII STERLING PLAZA, LLC, KBSIII ONE WASHINGTONIAN, LLC, KBSIII TOWERS AT EMERYVILLE, LLC, KBSIII TEN ALMADEN, LLC, KBSIII LEGACY TOWN CENTER, LLC, and...