no reduced rate of contributions to a reserve account is permitted to a person (or group of persons) having individuals in his (or their) employ unless—

(A) compensation has been payable from such account throughout the year preceding the computation date, and

(B) the balance of such account amounts to not less than five times the largest amount of compensation paid from such account within any 1 of the 3 years preceding such date, and

(C) the balance of such account amounts to not less than 2½ percent of that part of the payroll or payrolls for the 3 years preceding such date by which contributions to such account were measured, and

(D) such contributions were payable to such account with respect to the 3 years preceding the computation date; and