Tax finance question?

1. Suppose that you currently earn taxable income of $100,000 per year. You are subjected to a marginal tax rate of 45 percent. Currently, your average tax rate is 30 percent. (a) How would you calculate annual tax. (b) how would you calculate the extra tax that you would pay per year if your annual income increased to 120,000? (c) what is your average tax rate when your annual income is $120,000?