The first piece of the piecewise function is defined as \( f(x) = 2.5x \) for \( 0 \leq x \leq 20 \). This means that \( f(x) \) is valid and graphed for all \( x \) values from 0 to 20, inclusive.
The last point graphed on this piece of the function would be at the upper bound of the interval, which is when \( x = 20 \). To find the corresponding \( f(x) \) value at this point, we calculate:
\[ f(20) = 2.5 \times 20 = 50. \]
Therefore, the last point graphed on the first piece of the function is \( (20, 50) \).