As shown in the figure, B is the test site, AE is the road direction, BC is perpendicular to AE, ∠ EAB = 30, BC = 0.866 (the opposite side of 30 is half of the hypotenuse), so we can get AC =1.499955999 =1.5 from Pythagorean theorem or trigonometric function.

BD=BE= 1

So CD=0.500043998 1=0.5.

So AD= 1

Time? t= 1/ 12*60=5min？ In other words, no signal was received after 5 minutes.

Duration? t = DE/ 12 = 1/ 12 * 60 = 5min？ Five minutes.