A total of 20 amounts are entered on a spreadsheet that has 5 rows and 4 columns; each of the 20 positions in the spreadsheet contains one amount. The average (arithmetic mean) of the amounts in row i is {R}_{i} (1 \leq i \leq 5). The average of the amounts in column j is Cj (1 \leq j \leq 4). What is the average of all 20 amounts on the spreadsheet?
(1) {R}_{1}+{R}_{2}+{R}_{3}+{R}_{4}+{R}_{5}={550}
(2) {C}_{1}+{C}_{2}+{C}_{3}+{C}_{4}={440}