Electric breakdown (sparks) occur in air if the electric field reaches 3×106 N/C. At this field strength, free electrons present in the atmosphere are rapidly accelerated to such large speeds that upon impact with atoms they knock electrons off of the atom and thus generate an avalanche of electrons. How far must a free electron move under the influence of the above electric field if it is to attain a kinetic energy of 3×10-19 J(which is sufficient to produce ionization)?