a)
Pp = 2*5 = 10cm^2
Pb = (5+2+5+2)*5 = 14*5 = 70cm^2
Pc= 2Pp + Pb= 2*10cm^2 + 70cm^2 = 20cm^2 + 70cm^2 = 90 cm^2
b)
Pp = 1/2 * 3*4 = 6cm^2
Pb = (3+4+5)*4 = 12*4 = 48cm^2
Pc = 2*6cm^2 + 48cm^2 = 12cm^2 + 48cm^2 = 60cm^2
c)
Pp = 4*2 = 8dm^2
Pb = (4+3+4+3)*6 =14*6 = 84dm^2
Pc = 2*8dm^2 + 84dm^2 = 16dm^2 + 84dm^2 = 100dm^2
