<image>As shown in the figure, the polyline graph represents the functional relationship between the telephone charges $$y$$ (in yuan) and the call duration $$t$$ (in minutes) required by a certain telecommunications bureau. Based on the graph, fill in the blanks:



$$(1)$$ For a call duration of $$2$$ minutes, the telephone charge is ________ yuan;

$$(2)$$ For a call duration of $$5$$ minutes, the telephone charge is ________ yuan;

$$(3)$$ If $$t \geqslant 3$$, the functional relationship between the telephone charge $$y$$ (in yuan) and the call duration $$t$$ (in minutes) is ________.