How do you draw with a range of functions maple image

Have two functions:Function 1:When 0 <= x s1 when:f (x) = x – s1 – p1 function 2:When 0 <; = x s time:g (x) = s2 + p2 – x ask:1.how to use maple to draw these two functions, respectively Chart? 2.how to paint these two functions superposed Chart (for example:y = f (x) + g (x) of the image)? Thank you all for answers!

F:= x-> piecewise (0 <= x and x s1, x-s1-p1); s1:= 1; p1:= 2; plot (f); g:= proc (x) if 0 <= x and x <= s2 then p2 end if; if s2 <x then s2 + p2-x end if end proc; s2:= 3; p2 := 4; plot (g); plot (f + g);