A man can row at 12 km/h, and run at 5 km/h. He needs to get from a point A, on the south bank of a stretch of still water, to point B on the north bank of the water. The direct distance from A to B is 13 km, and the water is 12 km wide. He starts rowing with an angle theta between North and the direction in which he rows. Find an expression for the time he will take to get from A to B, in terms of theta.