More free points and (something else) for the first person to answer?

Can someone pls ! pls answer all. no explanation needed..

How to do this , and can some one explain

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 (%)