  Assuming SU(3) symmetry for the strong phases in the four decay modes
$B\rarrow \pi^-\pi^+, \pi^0 \pi^+, \pi^- K^+, \pi^- \bar{K}^0$ and ignoring the
relative small electroweak penguin effects in those decays, the weak phase
$\gamma$ and the strong phase $\delta$ can be determined in a model independent
way by the CP-averaged branching ratios of the four decay modes. It appears
that the current experimental data for $B\to \pi\pi$ and $\pi K$ decays prefer
a negative value of $\cos\gamma\cos\delta$. By combining with the other
constraints from $V_{ub}$, $B^{0}_{d,s}-\bar{B}^{0}_{d,s}$ mixings and indirect
CP-violating parameter $\epsilon_K$ within the standard model, two favorable
solutions for the phases $\gamma$ and $\delta$ are found to lie in the region:
$35^{\circ}\alt\gamma\alt 62^{\circ}$ and $106^{\circ}\alt \delta \alt
180^{\circ}$ or $86^{\circ}\alt\gamma\alt 151^{\circ}$ and
$0^{\circ}\alt\delta\alt 75^{\circ} $ within 1$\sigma$ standard deviation. It
is noted that if allowing the standard deviation of the data to be more than
1$\sigma$, the two solutions could approach to one solution with a much larger
region for the phases $\gamma$ and $\delta$. Direct CP asymme try
$a_{\epsilon''}^{(\pi^- K^+)}$ in $B\rarrow \pi^-K^+$ decay can be as large as
the present experimental upper bound. Direct CP asymmetry
$a_{\epsilon''}^{(\pi^+\pi^-)}$ in $B\rarrow \pi^-\pi^+$ decay can reach up to
about 40% at 1$\sigma$ level.
