[□]
[□=□]
[!□]
In fact , combined with other data , this nebula 's detectable shift over a three year period allows the expansion age of its bright inner shells to be estimated at only around 1,000 years while its distance can be gauged at about 3,000 light-years . The following table identifies the likely number of records that will be involved and the estimated growth rate per year for the sheet music and pictures collections . The low end of this range represents a 35 percent reduction in the estimated annual adverse events and the high end represents a 100 percent reduction . The duty section , in command of the Duty Officer , mounted and manned the anti-aircraft guns in accordance with the ship 's Air Raid Bill , and it is estimated that the guns were firing in about four minutes .