In an N bit flash ADC, the analog voltage is fed simultaneously to  comparators. The output of the comparators is then encoded to a binary format using digital circuits. Assume that the analog voltage source (whose output is being converted to digital format) has a source resistance of 75 Ω as shown in the circuit diagram below and the input capacitance of each comparator is 8pF. The output must settle to an accuracy of 1/2  LSB even for a full scale input change for proper conversion. Assume that the time taken by the thermometer to binary encoder is negligible.

If the flash ADC has 8 bit resolution, which one of the following alternatives is closest to the maximum sampling rate?