University of Birmingham, United Kingdom published a paper on Knapsack problem in what year?
Mention the year in which University of Birmingham, United Kingdom published a paper on Knapsack problem.
SELECT DISTINCT ?answer WHERE { <https://dblp.org/rec/conf/gecco/AlYahyaR15> <https://dblp.org/rdf/schema#authoredBy> ?x . ?x <https://dblp.org/rdf/schema#primaryAffiliation> 'University of Birmingham, United Kingdom' . <https://dblp.org/rec/conf/gecco/AlYahyaR15> <https://dblp.org/rdf/schema#yearOfPublication> ?answer }
<https://dblp.org/rec/conf/gecco/AlYahyaR15>