(a) Let the area be A m2
Average power per square meter = 200 W
Useful electrical energy produced per square meter,
= 20/100 x 200 = 40 Watt
Energy required by the family = 8 kW = 8000 watt
Hence, A = 8000/40
= 200 m2
(b) This area is comparable to that of a roof of a house of 14 m x 14 m.