To determine the last point graphed on the first piece of the function, \( f(x) = 2.5x \), let's first identify the domain for this piece of the function.
The first piece of the function is defined for \( 0 \leq x \leq 20 \). The last point in this domain would occur at \( x = 20 \).
Now, we can calculate the value of the function at this point:
\[ f(20) = 2.5 \times 20 = 50 \]
Thus, the last point graphed on the first piece of the function is \( (20, 50) \).