Expand the following: \begin{align} &\cssId{Step1}{{ n_T = 12 triangles equilàters}}\\[3px] &\cssId{Step2}{→ p_T = n_T · 3 b}\\[3px] &\cssId{Step3}{Example Selectivitat → p_T = 10,8 m}\\[3px] \end{align}