  Scattering problem of the $uudd{\bar s}$ system, in the standard
non-relativistic quark model of Isgur-Karl, is solved for the first time, by
treating the large five-body modelspace including the $NK$ scattering channel
accurately with the Gaussian expansion method and the Kohn-type coupled-channel
variational method. The two-body interaction that reproduces observed
properties of ordinary baryons and mesons is applied to the pentaquark system
with no additional adjustable parameter. The five-body wave function calculated
has the correct asymptotic form in its the scattering-channel component and
describes $qq$ and $q{\bar q}$ correlations properly. The $NK$ scattering phase
shift calculated shows no resonance in the energy region of the reported
pentaquark $\Theta^+(1540)$, that is, at 0-500 MeV above the $NK$ threshold
($1.4-1.9$ GeV in mass). The phase shift does show two resonances just above
500 MeV: a broad ${1/2}^+$ resonance with a width of $ \Gamma \sim~110$ MeV
located at $\sim~520$ MeV ($\sim~2.0$ GeV in mass) and a sharp ${1/2}^-$
resonance with $\Gamma=$0.12 MeV at 540 MeV. Properties of these states are
discussed.
