11 When Fred joined a computer firm his salary was \(\pounds 28000\) per annum. In each subsequent year he received an annual increase of \(12 \%\) of his previous year's salary.
- State Fred's salary for each of his first 3 years with the company. State also the common ratio of the geometric sequence formed by his salaries.
- How much did Fred earn in the tenth year?
- Show that the total amount Fred earned over the ten years was between \(\pounds 400000\) and £500000.
- When Fred joined the computer firm, his brother Archie set up a plumbing business. He earned \(\pounds 35000\) in his first year and each year earned \(\pounds d\) more than in the previous year. At the end of ten years, he had earned exactly the same total amount as Fred. Calculate the value of \(d\).