A young person has very particular tastes: she always has one luxury pizza and a six-pack of Lacroix water, every day, no matter what. The six-pack of Lacroix always costs $5, and the pizza usually costs $15. She lives on a weekly food budget of $140. If the price of pizza suddenly rises to 15.8, by how much will her welfare change? If the answer is that it will go down by 10.5%, then just write -0.105. Do not use a percent sign. Use three decimals in your answer. [Hint: welfare is the number of days of nourishment that she can afford with her weekly budget. It is possible that she can afford a fractional number of days of nourishment, such as 6.23]