Answer
a.
numerical
b.
Input Description: the year
Input Unit: years
Output Description: national debt
Output Unit: trillion dollars
c.
function
d.
x (year)
↓
Rule f
↓
f(x) (trillion dollars)
Work Step by Step
a. The representation is numerical because a table of the data is provided.
b. The input is years and the output is the national debt, because if you input the year you will get the debt for that year as output.
c. The relation is a function because for each year there is only one number for debt.
d. Draw an input/output diagram.