8The following shall be substituted for paragraph 6(2) of Part I of Schedule 4 to the Act of 1972—
“(2)If a farmer’s goods vehicle or a showman’s goods vehicle has a relevant maximum weight or a relevant maximum train weight, the annual rate of duty applicable to it shall be—
(a)if that weight does not exceed 75 tonnes, £90;
(b)if that weight exceeds 75 tonnes but does not exceed 12 tonnes, £135 in the case of a farmer’s goods vehicle and £90 in the case of a showman’s goods vehicle; and
(c)if that weight exceeds 12 tonnes, the appropriate Part II rate.”