Aprincipal of 3400 is invested at 6.5% interest, compounded annually. how many years will it take to accumulate 8000$ or more in the account

Acompany that manufactures and sells guitars made changes in their product range. from the start they had 20 models. then they reduced the number of models to 15. as a result, the company enjoyed a 10% increase in turnover. - how much did the stock level change? in (%)