The first piece of the piecewise function is defined as \( f(x) = 2.5x \) for the interval \( 0 \leq x \leq 20 \). The last point graphed on this piece occurs at the upper limit of this interval, which is \( x = 20 \).
To find the corresponding value of \( f(x) \) at this point:
\[ f(20) = 2.5 \times 20 = 50 \]
Thus, the last point graphed on the first piece of the function is \( (20, 50) \).