how many railway lines go through the station maintained by metropolitan transit authority of harris county ?
SELECT DISTINCT COUNT attr_open var_uri attr_close where brack_open var_x dbo_owningOrganisation dbr_Metropolitan_Transit_Authority_of_Harris_County sep_dot var_x dbo_servingRailwayLine var_uri sep_dot var_uri a dbo_RailwayLine brack_close