The first piece of the piecewise function is \( f(x) = 2.5x \) for \( 0 \leq x \leq 20 \). The last point graphed on this piece would be when \( x \) reaches its upper limit, which is \( x = 20 \).
To find the corresponding \( f(x) \) value:
\[ f(20) = 2.5 \times 20 = 50 \]
Thus, the last point graphed on the first piece of the function is \( (20, 50) \).