how do i know if Vc(0+) or Vc(0-) is zero?
The problem is quite simple when split into two parts.


With the switch in the position shown you have the capacitor in parallel with the lower resistor of a potential divider. The capacitor will charge up to the potential divider voltage. All you have to do is calculate what that voltage is.
After the switch is thrown you have a simple C-R discharge. The time constant is given by \$ \tau = RC \$ and you should know (or learn if you don't) the following for a charge or discharge curve:


At t = 1&tau; the capacitor voltage will have reduced by 63%.
At t = 3&tau; the capacitor voltage will have reduced by 95%.
At t = 5&tau; the capacitor voltage will have reduced by 99%.





Figure 1. RC discharge from 9 V. Source:[http://electronicsclub.info].

So figure out the RC time constant and plot those three points and draw the curve with Y-axis from 0 to the voltage calculated in step 1 and the X-axis going from -2 to +10 s as instructed in the question.

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