Sharon has opened a new startup company in web design. Within the first month of business, the startup agrees to maintain an accounting firm’s website in exchange for someone doing their tax returns.
Which of the following principles of economic interaction best describes this scenario?

1-Markets allocate goods effectively.
2-When markets do not achieve efficiency, government intervention can improve overall welfare.
3-Trade can make everyone better off.
4-All costs are opportunity costs.

trade can make everyone better off.

Explanation:

The aim of trade is to make all parties involved better off than they were before the trade occured. For example in international trade a country sells items they have reduced cost producing, while they buy items that will be expensive for them to produce.

In this instance the web startup is offering to give the accounting firm a service they have (web hosting) for tax return service.

Everyone is better off at the end of the day because they obtained a service they could not perform alone.

3) Trade can make everyone better off.

Explanation:

In this case, Sharon's opportunity cost of providing internet services to the accounting firm are lower than the actual costs of paying for the accounting services. The same happens to the accounting firm, whose costs of providing the accounting service are much lower than the costs of paying for internet related services.

So both are benefiting because they are trading the service in which they hold a comparative advantage and they receive a service with a high opportunity cost for them.

sound is invisible, but sometimes we can feel it. when a kettle-drum is thumped with a stick that time the tight drum skin moving up and down very quickly for some time and then it pumped sound waves into the air. loudspeakers also work in a similar manner.

components of a speaker:

electromagnet

in order to translate an electrical signal into an audible sound, an electromagnet is used in looudspeakers

  suspension

suspension is used to   center the voice coil in the gap of the magnet and it exerts a restoring force to keep it there. suspension is used to limits the maximum mechanical excursion of the diaphragm and voice coil.

voice coil

voice coil is a coil of wire which is attached to the apex of a loudspeaker cone. it provides the motive force to the cone by the reaction of a magnetic field to the current passing through it.

cone

in a   loudspeaker, a   thin, semi-rigid membrane attached to the voice coil, which moves in a magnetic gap due to which it vibrates   and produced sound. it is known as diaphragm and it can also be called a cone, though not all speaker diaphragms are cone-shaped.

surround

surround is also known as front suspension. surround is used to join the cone to the chassis. together with the suspension it controls the cone excursion, and it is also used to   determine how energy which is   travelling through the cone is absorbed, and how the speaker limits when it reaches the ends of its travel.

dustcap

dustcap is used to protect the voice coil from dust and dirt. it is a part of the cone.

how speaker work

the outer part of the cone is fastened to the outer part of the loudspeaker's circular metal rim. the inner part is fixed to   voice coil that sits just in front of a permanent magnet . when loudspeaker is hooked up to a stereo, electrical signals feed through the speaker cables into the coil. it will convert the coil into an electromagnet magnet . when electricity flows back and forth in the cables, the electromagnet either repels or attract the permanent magnet. this moves the coil back and forth, and it pull and push the loudspeaker cone. like a drum skin vibrating back and forth, the moving cone pumps sounds out into the air.in this way loudspeakers works.

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