Section 20 of the Principal Act is amended by omitting paragraph (b) and substituting the following paragraphs:

(b) in the case of a payment made before the commencement of building work having a value of less than $20 000 or such other amount as may be prescribed, is not more than 10% of the contract price; or

(c) in the case of a payment made before the commencement of building work having a value of $20 000 or more or such other amount as may be prescribed, is not more than 3% of the contract price.