the formula requires you to multiply base and height; we know the base is 320 but do not know height (which is the perpendicular segment connecting both sides of 320 feet)
we can create a right triangle by drawing the height which will have a hypotenuse of 160 and we know the angle across from the height is 49° (180 minus twice 131, divided in half)
therefore, we can use the law of sines to find height: