Shannon theorem and equation Eb/N0
You can calculate the data rate from Shannon's channel capacity equation since the SNR and the bandwidth are known.  Applying these values yields a maximum channel capacity of 9.3 Mbits/second.  Since your effective data rate is specified as 80% of that, your data rate is 7.4 Mbits/sec. Now you have all the values for your equation: S/N = 40 dB, R = 7.4 Mbits/sec and B = 700,000 Hz.