Correct option: (1) 27
Explanation:
When the capacitor is fully charged, the voltage across it is 15 V. After the switch is opened, it discharges through a resistor combination equivalent to 5.33 Ω. The equation describing the voltage on the capacitor is 15 exp / 2 (− t / RC ), which yields t = (5.33) (2.5) In (15 / 2) 27μs.