local q = io.read("*n")
for iq = 1, q do
  local p, k = io.read("*n", "*n")
  local z = 0
  local rate = 1
  for i = 1, k - 1 do
    z = z + i * rate * p
    rate = rate * (1 - p)
  end
  z = z + rate * k
  print(z)
end