Why is opportunity cost and scarcity important in economics?I want to know both of them separetely why they important in economics

There are limits to the quantity available of every
resource that is utilized in the economy. This is what leads to all goods and services
having a price. If there was no scarcity of resources, everything would be available for
free.

Opportunity cost is related to scarcity as neither
the consumer nor the producer has an unlimited resource of anything. Whenever any
transaction is carried out each party gives the other something that they have a limited
quantity of.

For example consider a person buying a car.
The buyer is spending money that could have been instead used each time the person hired
a taxi. By using a taxi the person would not have to drive the car herself and would be
assured of reaching the destination without putting in any effort. The opportunity cost
of buying the car is the services provided by a taxi. Only if the buyer feels that the
utility of having a personal vehicle is more than the utility of using a taxi does it
make sense to buy the car.

Similarly, the car dealer is
given some money by the buyer for the car. The opportunity cost for the dealer here is,
as an example, the amount that the car would have been sold for had it been exported. If
the dealer would have got a price for the car that is more than what was spent in
transporting the car to the foreign buyer, it does not make any sense to sell the car to
this buyer. The excess that the dealer could have earned is the opportunity cost of
selling the car here.