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 Ri (1 ≤ i ≤ 5). The average of the amounts in column j is Cj (1 ≤ j ≤ 4). What is the average of all 20 amounts on the spreadsheet? (1) R1 + R2 + R3 + R4 + R5 = 550 (2) C1 + C2 + C3 + C4 = 440 | 
