See the illustration. If a charged capacitor is connected to a coil by closing a switch, energy is transferred to the coil and then back to the capacitor in an oscillatory motion. The voltage V (in volts) across the capacitor will gradually diminish to 0 with time t (in seconds).

(a) Graph the function relating V and t:

(b) At what times t will the graph of V touch the graph of y = e^-t/3? When does the graph of V touch the graph of y = e^-t/3? 

(c) When will the voltage V be between -0.4 and 0.4 volt?

cos (t ),. 0