(16 points) The switch in the circuit has been in the left position for a long time. At $t = 0$ it moves to the right position and stays there.\
a) Write the expression for the capacitor voltage, $v(t)$, for $t \ge 0$\
b) Write the expression for the current through the 40 $k\Omega$ resistor, $i(t)$, for $t \ge 0^+$