Answer: Time value of money
Explanation:
Based on the information given in the question, the concept that Micah is trying to teach Roberta is referred to as the time value of money.
The time value of money simply means that the money that an individual has presently is of more value than the same amount that the person will receive in the future. It is believed that money can generate interest. This is what is discussed in the question as it is believed that the money should be invested rather than storing it under the matress where it will not generate an interest.
