This problem requires that Java Script be enabled Below is an "oracle" function. An oracle function is a function presented interactively.
When you type in an value, and press the --f-- button and
the value appears in the right hand window. There are three lines, so you can easily calculate
three different values of the function at one time.

The function f(t) represents the height in feet of a ball thrown into the air, seconds after it has been thrown.
Calculate the velocity 0.8 seconds after the ball has been thrown.