(1) the number obtained by multiplying the area in square metres of the floor of the conveyance by;(a) 5.25, where the surface of the floor is 1.86 m2 (20 ft2) or less;
(b) 6.25, where the surface of the floor is greater than 1.86 m2 (20 ft2) but less than 4.64 m2 (50 ft2);
(c) 7.1, where the surface of the floor is 4.64 m2 (50 ft2) or more; and