$100 is not enough

What about those nouns?

•   There is 2 seconds/minutes/hours.    2 seconds/minutes/hours are not enough.
•   There are 2 days/weeks/years.         2 days/weeks/years are not enough.

thanks 

When you think of a period of time, a specific distance, or an amount of money, you can think of it as one unit.

$100 is not too much to pay. Fifteen miles is not too far to travel. Four hours is not too long to wait. These are the equivalent of "The amount of $100 is..." and "The distance of 15 miles is..." and "The period of four hours is..."

"There is two seconds" is simply not a natural thing to say.

What questions remain unanswered?