386 is entitled to retired pay based upon the grade to which advanced. Such retired pay shall be at the rate of 2% percent of the basic pay of the grade to which advanced, determined by the same period of service used to determine the basic pay of the grade upon which his retainer pay is based, multiplied by the number of years of service creditable for his retainer pay at the time of retirement, but the retired pay may not be more than 75 percent of the basic pay upon which the computation of retired pay is based. (d) A member who is advanced on the retired list under this section from the grade of warrant officer, W - 1, or from an enlisted grade to a commissioned grade, and who applies to the Secretary within three months after his advancement, shall, if the Secretary approves, be restored on the retired list to his former warrant officer or enlisted grade, as the case may be. A member who is restored to his former grade under this subsection is thereafter considered for all purposes as a warrant officer, W - 1, or an enlisted member, as the case may be. § 6152. Emergency shore duty: advance of funds Under such regulations as the President approves, the Secretary of the Navy may, to meet necessary expenses, advance funds to members of the naval service detailed on emergency shore duty. The funds advanced may not exceed the reasonable estimate of expenses to be incurred for which reimbursement is authorized. § 6153. Shore patrol duty: payment of expenses An officer, midshipman, or cadet of the naval service who is assigned to shore patrol duty away from his vessel or other duty station may be paid his actual expenses. § 6154. Mileage books: commutation tickets The Secretary of the Navy may buy such mileage books, commutation tickets, and other similar transportation tickets as he considers necessary, and he may furnish them to persons ordered to perform travel on official business. Payment for those tickets before the travel is performed is not an advance of public money within the meaning of section 529 of title 31. § 6155. Uniforms, accouterments, and equipment: sale at cost Under such regulations as the Secretary of the Navy prescribes, uniforms, accouterments, and equipment shall be sold by the United States at cost to officers and midshipmen of the naval service and, wlien the Coast Guard is operating as a service in the Navy, to officers of the Coast Guard. § 6156. Uniform: sale to former members of the naval service (a) Under such regulations as the Secretary of the Navy prescribes, exterior articles of uniform may be sold to a person who has been discharged from the naval service honorably or under honorable conditions. This section does not modify section 772 or 773 of this title. (b) Money received from sales under this section shall be covered into the Treasury to the credit of the appropriation out of which the articles were purchased.