If the rate constant at 20 degrees CELSIUS IS 4.3(10^-5). How long would it take for 83% of the compound to decompose ?

If the rate constant at 20 degrees CELSIUS IS 4.3(10^-5). How long would it take for 83% of the compound to decompose ? if the rate constant is 9.0(10^-4) at 55 degrees Celsius what will the activation energy be?