How many years after Davydova's second son was born did she become Head Coach at Gemini Gymnastics?
return Davydova 's second son was  born ;return Davydova become Head Coach at Gemini Gymnastics ;return year of #1 ;return year of #2 ;return the  difference of #4 and  #3
['select', 'select', 'project', 'project', 'arithmetic']