please i need some help can i please have the formula on how they calculated the forecast 2015 please helppp

A F G B. C D E Actual Window Fan Demand and Forecast 1 2 . 00 Work Month Days 2011 2012 2013 3 1 21 61,294 44,261 35,720 4 2 20 63,659 71,182 42,846 5 3 22 17,144 52,895 27,772 6 4 21 30,831 47,786 56,943 5 20 23,763 43,688 35,287 8 6 22 19,001 11,452 35,631 7 22 20,011 50,165 66,414 10 8 21 22,070 51,648 34,121 9 21 17,534 24,537 53,058 12 10 22 59,568 45,899 82,018 13 19 92,429 51,087 66,824 12 14 21 81,020 61,272 46,460 15 Totals 252 508,324 541,060 597,906 42,360 16 Monthly Avg. 49,826 45,088 2015 2014 Forecast 69,238 52,628 73,816 62,876 34,858 33,167 40,519 44,020 18,746 30,371 20,989 21,768 39,405 43,999 56,888 41,182 38,232 33,340 75,578 65,766 75,674 71,504 67,821 64,143 611,764 564,764 50,980 47,064 9