RC circuit analysis involving input signal as step function.?

I am having trouble with this problem it says a input signal vc(t) is a step function which equals zero for t<0 and equals 2.0 V for t>or=0 for the a series circuit with a input voltage of 2 volts connected to a switch then a 10k resistor and lastly a 1.6nF capacitor leading back to ground. Assume there is no charge on the capacitor when the switch is closed. Determine vc(t) the voltage across the capacitor. I have found the equation vc(t) = [1-e^(-t/RC)] and have found an upper and lower limit of 2 and 1 but I don't understand where to go from there any help would be appreciated because I have read the lecture and book several times without any luck Thanks in advance for any help.