The value of the action potential -- how much greater the electric potential is inside the axon as compared to outside the axon -- is around 30 mV for the average neuron in humans. If the length constant of an axon is about 2 mm, at what distance x (to the nearest tenth of a mm) from the end of the axon where this action potential is applied would the potential difference across the membrane become less than 3.4 mV (which is a very weak signal)