The first piece of the piecewise function is given as \( f(x) = 2.5x \) for the interval \( 0 \leq x \leq 20 \).
The last point graphed on this segment corresponds to the upper endpoint of the interval, which is \( x = 20 \).
To find the function value at this point, we can substitute \( x = 20 \):
\[ f(20) = 2.5 \times 20 = 50 \]
Thus, the last point graphed on the first piece of the function \( f(x) = 2.5x \) is \( (20, 50) \).
So, the answer is: (20, 50).