Bert earns $35,000 gross annual salary. in bert's jurisdiction there is a progressive tax system with rules as follows: any amounts earned up to $20,000 are taxed at x%. any amounts earned beyond $20,000 are taxed at 20%. given that bert pays $4,500 per annum in income tax, calculate x. give your answer to the nearest tenth of a percent. do not include the percent symbol in your answer.