In this task, you need to answer the given multiple-choice question on the general math. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.

Problem: a customer bought a product at the shop . however , the shopkeeper increased the price of the product by 10 % so that the customer could not buy the required amount of the product . the customer managed to buy only 80 % of the required amount . what is the difference in the amount of money that the customer paid for the second purchase compared to the first purchase ? 
Options: a ) 10 % , b ) 12 % , c ) 14 % , d ) 16 % , e ) 18 %
b

Problem: for any integer k greater than 1 , the symbol k * denotes the product of all integers between 1 and k , inclusive . if k * is a multiple of 315 what is the least possible value of k ? 
Options: a ) 5 , b ) 7 , c ) 9 , d ) 11 , e ) 13
b

Problem: two quarts containing 2 ⁄ 3 water and 1 ⁄ 3 formula are mixed with 3 quarts containing 3 ⁄ 8 water and 5 ⁄ 8 formula . approximately what percent of the combined 5 - quart mixture is water ? 
Options: a ) 40 % , b ) 45 % , c ) 50 % , d ) 55 % , e ) 60 %

c