What is this kind of equation called, and does anyone know how i would put that into a graphing calculator as a y function?

The function 

   

is considered a piecewise function.

which piece the function uses depends on what the input is.

if t is between 0 (inclusive) and 3 (exclusive), i.e.  ,  then the function uses the piece (horizontal line at y=250) 

if t is between 3 (exclusive) and 7 (inclusive), i.e.  , then the function uses the piece  (horizontal line at y=2000).



if you want to enter this into a ti84  calculator, you would enter the following:
(refresh if the below does not display properly)

   

basically multiply each piece by their constraints, and add the pieces together.

the < and  ≤ symbols, and the  operator  you would find the test menu, which is above the math button ( you would find under 2nd > test > logic)

If i'm correct the answer is $15.97