Discovery or invention of USA•ether.- due to its misuse, the sale requires a prescription. Is used in some surgical

procedures, although actually its use is restricted due to misuse.•Phone.- most people have phones at home because it´s not so expensive to have. Is a

great invention because is easier for people to communicate but, at the beginning was not so available and not easy to have one at home.

•Cash machine.- more accurate accounts and for use in too large accounts have greater accuracy and reliability. Its use became more accessible to perform accounts and record

accounts in stores.•Automobile.- not all the people could buy one and, only until its mass production became accessible for purchase. Made easier in the short and long transportation

distances and eliminated the dependence on other modes of transportation.•Microwave.- is not too expensive to purchase but, its is too expensive for the power

consumption, one hour of use is around 13 pesos..their use has facilitated the process of heating food and save time in cooking.

•Computer.- if you need to use a computer you can go to a cyber store. Most people know or want to learn to use it because it is necessary, also as a communication way.

•Polio vaccine.- is so available without affect the economy of the people if has a medical care agreement; otherwise it can sometimes be expensive. It eliminates the risk of

bulbar polio and post polio syndrome.•Electronic poker calculator.- it is not too expensive to acquire one. It helps to have

more accurate calculations.•Artificial heart.- is expensive but, for urgency situation can help to save a life. It is used

on a temporary basis in some heart transplant candidates who are awaiting for a heart donor, but urgently needed to replace his heart and he is very ill.