Select the appropriate answer
1. If \(x_i\) are the class marks, \(f_i\) are the corresponding frequencies, and \(\overline x\) is the mean of the grouped data, then \(\sum(f_ix_i- \overline x)\)
2. While finding the mean by the step-deviation method, if \(a\) is the assumed mean, \(h\) is the class size and \(x_i\) is the class mark, then \(u_i\) is