(Solved): 3. The street-lights at \( A \) and \( B \) are suspended from the two poles as shown. If each ligh ...

3. The street-lights at \( A \) and \( B \) are suspended from the two poles as shown. If each light has a weight of \( 45 \mathrm{lb} \), determine the tension in each of the three supporting cables and the required height \( h \) of the pole \( D E \) so that cable \( A B \) is horizontal. (Note: Although the figure looks 3-D, the traffic lights, supporting cables and the two poles are in the same plane. Hence, this is a 2-D equilibrium problem.)