According to the provisions of IPC what is the liability of A, a police officer, who abets the commission of robbery?

Section 116. Abetment of offence punishable with imprisonment—if offence be not committed—Whoever abets an offence punishable with imprisonment shall, if that offence be not committed in consequence of the abetment, and no express provision is made by this Code for the punishment of such abetment, be punished with imprisonment of any description provided for that offence for a term which may extend to one-fourth part of the longest term provided for that offence; or with such fine as is provided for that offence, or with both; If abettor or person abetted be a public servant whose duty it is to prevent offence.—and if the abettor or the person abetted is a public servant, whose duty it is to prevent the commission of such offence, the abettor shall be punished with imprisonment of any description provided for that offence, for a term which may extend to one-half of the longest term provided for that offence, or with such fine as is provided for the offence, or with both. (c) A, a police-officer, whose duty it is to prevent robbery, abets the commission of robbery. Here, though the robbery be not committed, A is liable to one-half of the longest term of impris­onment provided for that offence, and also to fine.