For 200m with a directional pair of antennas then band B will certainly be adequate in terms of power. It will also reduce others trying to intercept it
An initial scan using a inSSIDer will show how much use there is on the 5MHz spectrum - if it is busy then move to band C and get a license.
I wonder if the OP has also considered splitting the cost with immediate neighbours - provided the service is forecast to be fast enough.
M H C
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