backlog backlog decreased in 2015 compared to 2014 primarily due to sales being recognized on several multi-year programs ( such as hmsc , nisc iii , ciog and nsf asc ) related to prior year awards and a limited number of large new business awards . backlog decreased in 2014 compared to 2013 primarily due to lower customer funding levels and declining activities on direct warfighter support programs impacted by defense budget reductions . trends we expect is&gs 2019 2016 net sales to decline in the high-single digit percentage range as compared to 2015 , primarily driven by key loss contracts in an increasingly competitive environment , along with volume contraction on the segment 2019s major contracts . operating profit is expected to decline at a higher percentage range in 2016 , as compared to net sales percentage declines , driven by higher margin program losses and re-compete programs awarded at lower margins . accordingly , 2016 margins are expected to be lower than 2015 results . missiles and fire control our mfc business segment provides air and missile defense systems ; tactical missiles and air-to-ground precision strike weapon systems ; logistics ; fire control systems ; mission operations support , readiness , engineering support and integration services ; manned and unmanned ground vehicles ; and energy management solutions . mfc 2019s major programs include pac-3 , thaad , multiple launch rocket system , hellfire , jassm , javelin , apache , sniper ae , low altitude navigation and targeting infrared for night ( lantirn ae ) and sof clss . mfc 2019s operating results included the following ( in millions ) : .

2015: net sales: 6770
operating profit: 1282
operating margins: -18.9
backlog at year-end: 15500
2014: net sales: 7092
operating profit: 1344
operating margins: -19
backlog at year-end: 13300
2013: net sales: 6795
operating profit: 1379
operating margins: -20.3
backlog at year-end: 14300

2015 compared to 2014 mfc 2019s net sales in 2015 decreased $ 322 million , or 5% ( 5 % ) , compared to the same period in 2014 . the decrease was attributable to lower net sales of approximately $ 345 million for air and missile defense programs due to fewer deliveries ( primarily pac-3 ) and lower volume ( primarily thaad ) ; and approximately $ 85 million for tactical missile programs due to fewer deliveries ( primarily guided multiple launch rocket system ( gmlrs ) ) and joint air-to-surface standoff missile , partially offset by increased deliveries for hellfire . these decreases were partially offset by higher net sales of approximately $ 55 million for energy solutions programs due to increased volume . mfc 2019s operating profit in 2015 decreased $ 62 million , or 5% ( 5 % ) , compared to 2014 . the decrease was attributable to lower operating profit of approximately $ 100 million for fire control programs due primarily to lower risk retirements ( primarily lantirn and sniper ) ; and approximately $ 65 million for tactical missile programs due to lower risk retirements ( primarily hellfire and gmlrs ) and fewer deliveries . these decreases were partially offset by higher operating profit of approximately $ 75 million for air and missile defense programs due to increased risk retirements ( primarily thaad ) . adjustments not related to volume , including net profit booking rate adjustments and other matters , were approximately $ 60 million lower in 2015 compared to 2014 . 2014 compared to 2013 mfc 2019s net sales increased $ 297 million , or 4% ( 4 % ) , in 2014 as compared to 2013 . the increase was primarily attributable to higher net sales of approximately $ 180 million for air and missile defense programs primarily due to increased volume for thaad ; about $ 115 million for fire control programs due to increased deliveries ( including apache ) ; and about $ 125 million for various other programs due to increased volume . these increases were partially offset by lower net sales of approximately $ 115 million for tactical missile programs due to fewer deliveries ( primarily high mobility artillery rocket system and army tactical missile system ) . mfc 2019s operating profit decreased $ 35 million , or 3% ( 3 % ) , in 2014 as compared to 2013 . the decrease was primarily attributable to lower operating profit of about $ 20 million for tactical missile programs due to net warranty reserve adjustments for various programs ( including jassm and gmlrs ) and fewer deliveries ; and approximately $ 45 million for various other programs due to lower risk retirements . the decreases were offset by higher operating profit of approximately $ 20 million for air and missile defense programs due to increased volume ( primarily thaad and pac-3 ) ; and about .

Questions:
what is the sum of the average backlog at year-end in 2014 and 2015?
what is the sum including the 2013 value?
what is that divided by 3?

Answers:
28800
43100
14367