How many years is the age range for estimated average requirements for women taking 18.0 mg/day?
return the  estimated average requirements for women taking 18.0 mg/day ;return the  age range in  years of #1 ;return the  highest of #2 ;return the  lowest of #2 ;return the  difference of #3 and  #4
['select', 'project', 'aggregate', 'aggregate', 'arithmetic']