ofdm bit rate with various subcarriers and symbol rate

An 1 MHz channel is divided into 52 sub channels of 300 kHz wide using OFDM. The system uses 48 subcarriers for data traffic and 4 channels for error correction and control. The basic symbol rate per subcarrier is 125 kS/s. Determine the following:
a. The overall bit rate with one 20 MHz channel, all subcarriers using 16-QAM.
b. The overall bit rate with one 20 MHz channel, 24 subcarriers using 64-QAM and 24 using 16-QAM.

I like do some math.
a. 20*1*48*125K*4=480M.
b. 20*1*24*125*4+20*1*125*6=600M