$($b$)$ Figure $1$ shows a timber$-$based struct$$ral system of a building. Taking into

consideration the functionality, durability, mechanical and physical

properties of timber, interpret the most suitable types of timber for the

following elements. Provide appropriate interpretation for each proposal.

$($i$)$

Rafter

$($ii$)$

Beam

$($ili$)$

Floor

$($iv$)$

Stairs

Wall