Compute the amount to be paid for each of the four separate invoices assuming that all invoices are paid within the discount period. \begin{tabular}{|l|rr|c|l|} \hline & \multicolumn{2}{|c|}{\begin{tabular}{c} Merchandise \\ (gross) \end{tabular}} & \multicolumn{1}{|c|}{ Terms } & Payment \\ \hline a. & $ & 6,400 & 2/10,n/60 & \\ \hline b. & $ & 22,100 & 1/15,n/90 & \\ \hline c. & $ & 77,800 & 1/10,n/30 & \\ \hline d. & $ & 13,500 & 3/15,n/45 & \\ \hline \end{tabular}