jennair gas stove installation model jds 98608aap

what size vent pipe should I use for a 12 foot distance to vent to the outside. I would go down through the floor to a 5 foot crawl space and out hoizontally. Is a right angle at this location or a 45 degree better. My exhaust fan has a 4 inch disharge. Would a four inch diameter pipe 12 feet long allow for proper venting? At the outside wall location, should I allow for a slight pitch downward, level or upward relative to the stove. Is there a flap to put on the end to keep out animals, wind ect.GTR from Ct.