Question:
Which employer did Derek Simpson work for in Mar, 1997?

Context:
 Derek Simpson works for Amalgamated Engineering and Electrical Union from Jan, 1992 to Jan, 2001. 
 Derek Simpson works for Firth Brown Steels from Jan, 1960 to Jan, 1966. 
 Derek Simpson works for Amalgamated Engineering Union from Jan, 1981 to Jan, 1992. 
 Derek Simpson works for Unite the Union from Jan, 2007 to Jan, 2010.

Answer:
Amalgamated Engineering and Electrical Union