Ok, let x be the tariff at any time t years.
When t = 0 (initial tariff), x = 0.413
When t = 1, x = 0.413 + (0.413 * 2.4%)
When t = 2, x = 0.413 + (0.413 * 2.4% * 2.4%)
So, when t = n, x = 0.413 + 0.413 * 2.4%^(n)
or
Ok, second part. Let y be the electricity output, with the same time, t years.
When t = 0, y = 1785
When t = 1, y = 1785 - (1785 * 0.5%)
When t = 2, y = 1785 - (1785 * 0.5% * 0.5%)
So, when t = n, y = 1785 - (1785 * 0.5%^ n)
or
Net income is then given by: income - tariff.
You can do that. I did the most part of the problem.