(b) (i) the making, product; importing, offering for sale, selling and using the (ii) stocking such product for the purposes o( offering for sale, selling or using; where the patent has been granted in respect of a process (i) the use of the process; (ii) the performance of any of the acts referred to in paragraph (a) in respect of a product obtained directly by means of the process. (3) Any owner of a patent shall, in addition to any other rights, remedies or actions available to him, have the right, subject to subsection (4) and section 22, to institute civil proceedings in damages against any person who infringes the patent by performing, without his agreement, any of the acts referred to in subsection (2) or who performs acts which make it likely that infringement will occur. (4) Any right under the patent shall not extend (a) to acts in respect of articles which have been put on the market in Mauritius or in any other country by the owner of the patent or with his consent, or by any other authorised party; (b) in respect of articles which have been put on the market in Mauritius or in any other country or imported into Mauritius; (c) to the use of articles on aircraft, land vehicles or vessels of other countries which temporarily or accidentally enter the airspace, territory or waters of Mauritius; or (d) to acts done only for research and experimental purposes relating to a patented invention; (e) to acts performed by any person who in good faith, before the filing or, where priority is claimed, the priority date of the application on which the patent is granted and in Mauritius, was using the invention. or was making effective and serious preparations for such use. (5) The right of any prior use referred to in subsection (4) may only be transferred to or devolve upon the enterprise or business, or with that part of the enterprise or business, in which the use or preparations for use have been made. 22. Duration (1) Subject to subsection (2), a patent shall expire 20 years after the filing date of the application for the patent. (2) In order to maintain the patent or patent application, an annual fee as may be prescribed shall be payable to the Controller for each year, following the year of the filing date. (3) If the annual maintenance fee is not paid in accordance with the provisions of subsection (2), the patent application shall be deemed to have been withdrawn and the patent shall lapse. 23. Exploitation by government or person thereby authorized