class Array

# File lib/ext.rb, line 61
def avg
  s, n = self.sum_with_number
  return s / n
end

# File lib/ext.rb, line 57
def sum
  s, n = self.sum_with_number
  return s
end

# File lib/ext.rb, line 66
def sum_with_number
  return nil, 0 if(self.size <= 0)
  s = nil
  n = 0
  self.each do |v|
    next if v.nil?
    if(s==nil)
      s = v
    else
      s += v
    end
    n += 1
  end
  return s, n
end