Burbank-based Shamrock Acquisition III Inc. has extended its $42-a-share cash tender offer for all of Polaroid Corp.'s common shares outstanding and the associated preferred stock purchase rights, to 5 p.m. Nov. 28 . . . Alaska Airlines flew its first flight as a scheduled international air carrier with Flight 30, a non-stop from San Francisco to Mazatlan, a resort city on the West Coast of Mexico . . . San Francisco-based Wells Fargo & Co. increased its quarterly common stock dividend to 75 cents and share from 60 cents, payable on Jan. 20, 1989, to shareholders of record Dec. 30 . . . The board of West Point-Pepperell of West Point, Ga. has postponed action under its shareholder rights plan while appealing a court decision invalidating a portion of the plan.