How do we determine the minimum value in solutions of maxima and minima ( like k, l, m and n are the percentage of people who take only one paper, exactly 2 papers, exactly 3 papers and all four papers respectively. k+l+m+n=100 - (1) k+2l+3m+4n=330 - (2) Subtracting 3 times equation 1 from 2, we get n = 30 + 2k + l So, the least value of n occurs when k and l are 0 and the least value is 30%.)