Shyam constructs a certain wall. working a special way and takes 12 days to complete it. The length of the wall (in metres) that he constructs on the ` n^th ` day, then `L_n = {(2n , 0 le n le 4 `) , (8 , for n = 5 ) , (3n - 7 , `6 le n le 12 `)