SEC. (B). A boat of this section shall be a lifeboat, of whaleboat form properly constructed of wood or metal, having inside and outside buoyancy apparatus together equal in efficiency to the buoyancy apparatus provided for a boat of section (A). At least one-half of the buoyancy apparatus must be attached to the outside of the boat. SEC. (C). A boat of this section shall be a lifeboat, properly constructed of wood or metal, having some buoyancy apparatus attached to the inside and (or) outside of the boat, equal in efficiency to one-half of the buoyancy apparatus provided for a boat of section (A) or section (B). At least one-half of the buoyancy apparatus must be attached to the outside of the boat. SEC. (D). A boat of this section shall be a properly constructed boat of wood or metal. SEC. (E). A boat of this section shall be a boat of approved construction, form, and material, and may be collapsible. (2) _Cubic capacity._--The cubic capacity of an open boat and of a deck boat of section (D) or section (E) shall be ascertained by multiplying the product of the length, breadth, and depth by 6, subject, however, to the following provisions: The length shall be measured from the foreside of the rabbet on the stem to the afterside of the rabbet on the sternpost, and the breadth shall be measured from the outside of plank to the outside of plank amidships. The actual depth shall be measured from the top of the gunwale to the top of the bottom plank next to the keel, but the depth used in calculating the cubic capacity shall not in any case exceed 3.6 feet; and if the actual depth measured is equal to or less than 3.6 feet, the depth used in calculating the cubic capacity shall not exceed 45 per cent of the breadth measured, as indicated above. If the oars are pulled in rowlocks, the bottom of the rowlock is to be considered as the gunwale in measuring the depth of the boat. If any question is raised requiring absolute accuracy, the cubic capacity of a boat shall be ascertained by Stirling's rule, subject to the foregoing provisions as to depth. (3) _Number of persons for boats._--(_A_) Subject to the provisions of paragraphs (_b_) (_c_) and (_d_) of this clause the number of persons[5] an open boat of section (A) shall be deemed fit to carry shall be the number of cubic feet ascertained as in rule (2) divided by 10, and the number of persons[6] an open boat of section (B) or section (C), or an open or decked boat of section (D) or section (E) shall be deemed fit to carry shall be the number of cubic feet ascertained as in rule (2) divided by 8. The space in the boat shall be sufficient for the seating of the persons carried in it and for the proper use of the oars.