Question

A voltage source e(t), which has a value of 2V at t=0, rises exponentially to a final value of 6V with a time constant of 3sec. Determine the expression for e(t).
I have possible answers
a) e(t)=(6-4e^(-t/3))u(t)
b) e(t)=6e^(-t/3)u(t)
c)e(t)=(2+4e^(-t/3))u(t)
d)e(t)(6-2e^(-3t))u(t)