11. Stocks of "Maloney & Co". On Monday, April 7, the stock of the "Maloney & Co" Trading House was worth 5 Anchurian dollars. Over the next six days, the stock did not fall in price or even rose, and by Sunday, April 13, the stock price reached 5 dollars and 14 cents. For the entire following week, the stocks did not rise and even fell in price so that on April 20, the stock was again worth 5 dollars.

a) (6th grade. 1 point). Provide an example of how the prices could have changed so that the average rate for the entire period from April 7 to April 20 was higher than 5 dollars and 9 cents but lower than 5 dollars and 10 cents.

b) (6th grade. 2 points). Reviewer A claims that the average stock price for the period from April 7 to April 13 was 10.5 cents lower than the average stock price for the period from April 14 to April 20. Reviewer B says that A is wrong. Who is right?
Solution. b) The lowest average stock price over the period from April 7 to April 13 is no less than $\frac{5+5+5+5+5+5+5.14}{7}=5.02$ dollars.

The highest average stock price over the period from April 14 to April 20 is no more than $\frac{5.14+5.14+5.14+5.14+5.14+5.14+5}{7}=5.12$ dollars. Thus, the difference between the average prices does not exceed $5.12-5.02$ dollars, which is 10 cents.

Answer: b) B is correct.