A parallel-plate air capacitor whose plates are separated by a distance d = 5.0 mm is first-charged to a potential difference V = 90 V and then disconnected from a dc voltage source. Find the time interval during which the voltage across the capacitor decreases by η = 1.0%, taking into account that the average number of ion pairs formed in air under standard conditions per unit volume per unit time is equal to nt = 5.0 cm-3 ∙ s-1 and that the given voltage corresponds to the saturation current.