Looks like an '88 ST400. Entry level Cannondale tourer. Capable bikes, they make nifty commuters.
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My bikes: '81 Trek 957, '83 Trek 720, '85 Trek 500, '85 Trek 770, '81 Merckx, '85 Centurion Cinelli, '85 Raleigh Portage, '92 RB-2, '09 Bianchi