Governmental Laws and Taxes

Someone owns a gift shop in a busy tourist hot spot. One day, he discovers a one-hundred dollar bill in his cash register that is counterfeit and cannot determine who gave it to him. If he brings it to a bank, they will certainly not accept it, resulting in a total loss of that money. Is it permitted for him to pass the bill on to someone else, such as an unsuspecting customer, who will likely never know the difference? Does it matter if that customer is a Jew or a non-Jew?

Reuven decided to build an extension next to Shimon’s property. When Shimon complains that Reuven’s construction violates the local zoning laws, Reuven responds that it is still permitted since it does not violate any of the halachos found in hilchos shechenim . Is Reuven correct or may Shimon prevent him from continuing the construction due to the local laws, and if so, how?

Whenever a certain person drives with his family, his wife insists that he drive exactly at the speed limit, since dina d’malchusa dina, and that is the law, even if no one else follows it. But his children respond that no one drives at the speed limit, everyone drives faster. Consequently, since another car may hit his car from behind, it could be dangerous not to drive faster than the speed limit. Who is right?

Someone went to the beach and lost an expensive watch of over $10,000. He was not sure if it was swept away by the water or lost in the sand. He looked for a little while, couldn’t find it, gave up, and left. His friend who accompanied him to the beach later decided that he would search for the watch. After searching for it in the sand, he finds it. May he keep it? Does it matter if he is having financial difficulties and the owner of the watch is wealthy and may not be particularly upset that it was lost?