Solve clearly

Existing infrastructure system which supplies a good/service to a city at a constant marginal cost MC = 5 hasjust reached its capacity C = 24. The price elasticity of the demand is O.38 and the demand is expected to grow at the (annuallycompounded) rate 2% a year. The government is considering a plan to permanently extend the capacity by 40%. The extension can be done at any time with a total cost (including upfront and future maintenance cost) discounted to the time when it comes into operation equivalent to 327. The interest rate is 3%. Determine the year during which the extension optimally comes in operation (it is the beginning of year 0 at the moment}