Suppose medians of two populations 1 and 2 are to be compared using Mann_Whitney rank sum test at 5% level of significance. Suppose independent random samples of sizes 10 each are drawn from populations 1 and 2, and suppose the data sets are used to test the null hypothesis of equality of medians of the two populations against the alternative that the median of population 1 is higher than the median of population 2. If sum of the ranks for sample values from population 1 is W =133 then the relevant test statistic U, is: n O a. 77 O b. 22 O c. 78 O d. 23