A uniform beam of length 12 ft and weight 300 lb is supported by a pin at A and a roller at B. A cable attached at point C (4 ft from A) runs over a smooth pulley at D and supports a 400 lb block as shown. If D is located 3 ft above and 5 ft to the right of C, what is the magnitude of the horizontal reaction force at pin A? A) 325 lb B) 340 lb C) 355 lb D) 370 lb