Should the Contractor neglect or refuse to pay, within five days after it falls due, any bill legitimately incurred by him hereunder (and for which he is to be reimbursed under Article 5), the Owner, after giving the Contractor twenty-four hours' written notice of his intentions so to do, shall have the right to pay such bill directly, in which event such payment shall not, for the purpose either of reimbursement or of calculating the Contractor's fee, be included in the cost of the work.