Reduce pollution so the environment can be clean
The Lion is an Evangelist sign of the power of the Evangelical messages, spiritual elevation, majesty and power, along with wisdom and intelligence (the winged lion is usually depicted with a book or bible), and as a messenger of God as described in the verse of The Apocalypse of St. John 4:7
The economic term is the opportunity cost.
The concept of opportunity cost is a relatively inexpensive and relative measure that involves people's preferences, so it varies from person to person. It is a question of comparing what is left over when making a decision.
In Katie's case, the opportunity cost of the money she saves to buy a car is what she fails to do with that money. For example, she stops investing in stocks, fails to make a trip, etc.
All decisions involve an opportunity cost. Taking another example, the opportunity cost of studying for the test at the end of the week is measured by the loss of leisure you would have. However, the decision to study for the test is chosen because it is more valuable.
