a dishonest milkman A buys 100L of milk from another dishonest milkman B for onward distribution. he retains 10Lof milk for personal use, adds water to make up the shortfall and sells the mixture at Rs 15/L, thereby making a profit of Rs 2.75/L on the quantity sold. if B had already diluted the milk with water in the ratio of milk:water::9;1 and he makes a profit of Rs1, the price /L of pure milk purchased by B is closest to?