How much carpet you need is found by taking length x width of the room. That gives you the square footage. Divide that by 9 and that gives you square yards.
15 by 14 is 210 Sq ft which is 23.33 yards If installation is 5$ a yard Pad is 3$ a yard. Carpet you get a 12 $ a yard carpet (med. Grade) So right at about 500$ is what you'd be looking at