Incentive contributions. If the permit granting authority grants a special permit for an increase in the maximum lot coverage intensity of use in a business or Commercial 1 through Commercial 6, said authority shall require the applicant to make a contribution into a Traffic Safety and Infrastructure Fund ("fund"). The rate of contribution shall be $3 per square foot of gross floor area of a building whose primary use shall be for office or retail space, and the rate of contribution shall be $1 per square foot of gross floor area of a building whose primary use will be for industrial, manufacturing, warehousing, product and material distribution or similar purposes. The primary use of a building or buildings, for the purpose of this section, shall be deemed to be office or retail use where the total square foot floor area used for office or retail purposes, considered either individually or where both uses are added together, constitutes more than 20% of the entire gross square foot area of the building or buildings in question. Otherwise, the primary use of the building or buildings shall be deemed for a use other than office or retail, and the rate of contribution shall be $1 per square foot of gross square foot area.