Sketch the graph of a function y= f(x) with the following properties:

lim f(x)= -infinity

x-->-infinity

lim f(x)= 4

x-->-1^-

lim f(x)=2

x-->-1^+

lim f(x)= infinity

x-->3^-

lim f(x)=1

x-->3^+

lim f(x)= infinity

x-->infinity