Asmall technology firm can either produce computer keyboards or mice. the company has a limited number of workers, so it can only spend 400 hours per week making these products. the company makes a profit of $8 per keyboard and $5 per mouse. if each keyboard requires four hours of labor, and each mouse takes two hour of labor, which of the following is true about the number of hours that can be spent making keyboards (k) and mice (m)?

Quick! a survey of 57 customers was taken at a bookstore regarding the types of books purchased. the survey found that 33 customers purchased mysteries, 25 purchased science fiction, 18 purchased romance novels, 12 purchased mysteries and science fiction, 9 purchased mysteries and romance novels, 6 purchased science fiction and romance novels, and 2 purchased all three types of books. a) how many of the customers surveyed purchased only mysteries? b) how many purchased mysteries and science fiction, but not romance novels? c) how many purchased mysteries or science fiction? d) how many purchased mysteries or science fiction, but not romance novels? e) how many purchased exactly two types of books?