(a) if he fails to provide the Bond

(a) if he fails to provide the Bonds and the Guarantee referred to in Clause 7 to the Authority within the time prescribed by the said clause; or (b) if without reasonable excuse he fails to commence the Works after receipt of the Authority's Letter of Acceptance or without reasonable cause he wholly suspends the carrying out of the design or construction of the Works before completion thereof; or (c) if despite previous warning in writing from the Engineer he fails to proceed regularly and diligently with the performance of his obligations under the Contract; or (d) if he refuses or persistently neglects to comply with a written notice from the Engineer requiring him to remove defective work or improper Plant, materials or goods and by such refusal or neglect the Works are materially affected; or (e) if the Contractor sub-lets the Contract;