What is this in excel??

B C 5 D E F G H J L N 0 2 Average Cells at Set Interval 3 Create a formulat that AVERAGES the cash flows using following two input cells (with result that will dynamically change when cells E5 and E6 are changed) 4 5 Beginning Mo to Start Caloulation 10 6 No of months to sum 18 7 8 Write Formula Here > 9 10 Month Cash Floy 11 1 $78 12 2 $75 13 3 $89 14 4 $43 15 5 $5 16 6 $8 17 7 $75 18 8 $40 19 9 $67 20 10 $19 21 11 $5 22 12 $22 23 13 $74 24 14 $87 25 15 $37 26 16 $92 27 17 $100 28 18 $25 29 19 $7 30 20 $18 21 $99 32 22 $81 33 23 $81 34 24 $30 35 25 $18 36 26 $77 37 27 $46 38 28 $99 39 29 $18 40 30 $7 41 31 $55 42 32 $31 43 33 $82 44 34 $22 45 35 $94 46 36 $14