Trace: list index

Line 1: prices = [4, 9, 2, 7]1prices = [4, 9, 2, 7]
Line 2: i = 12i = 1
Line 3: a = prices[i]3a = prices[i]
Line 4: i = len(prices) - 14i = len(prices) - 1
Line 5: b = prices[i]5b = prices[i]
Line 6: print(a + b)6print(a + b)

Fill in one row each time a line changes i, a or b, or prints something. The table already has the right number of rows. In each row, write only what that line changes; you can leave the other cells empty or copy their values down. Write values the way Python shows them: 3 and 3.0 are different, and text goes in quotes. In the output column, write exactly what appears on screen, with no quotes around it.