N = gets.to_i

N.times do
  t, u, l = gets.split.map(&:to_f)

  s = ->(v, t, m) { v * t + Rational(v ** 2, 20 * m) }
  ok = 0
  ng = 100_000

  100.times do
    v = (ok + ng) / 2.0
    x = s[v, t, u]

    if x <= l
      ok = v
    else
      ng = v
    end
  end

  puts "%.2f" % Rational(ok * 3600, 1000).floor(2)
end