Coherent orthogonal binary FSK modulation is used to transmit two equiprobable symbol waveforms s₁ (t) = acos 2^_$\pi$f₁ t and s₂ (t) = ^_$\alpha$cos 2^_$\pi$f₂ t, where ^_$\alpha$ = 4 mV. Assume an AWGN channel with two sided noise power spectral density ^{$\frac{N_0}{2}$} = 0.5 ^_x 10 W/Hz. Using an optimal receiver and the relation Q (v) = ^{$\frac{1}{\sqrt{2 \pi}} \int\limits_v^\infty$$e^{-u^2/2}$} du, the bit error probability for a data rate of 500 kbps is