a)
a = n
b = 6
Obw = a +a + b + b
Obw = n + n + 6+ 6 = 2n + 12
Obw = 2n + 12
b)
P = [tex]\frac{e*f}{2}[/tex]
e = 9
f = c
P = [tex]\frac{9*c}{2} = \frac{9c}{2} = 4,5c[/tex]
