The power from the Sun is intercepted by the cross-sectional area of the Earth pr2. Since C = 2pr then
Cross-section area= C2/4p = (40000X103)2/4p = 1.273X1014 m2 (This answer will be needed in question 2.)

 Solar intensity = 1.35 kW/m2
Total power = 1.273X1014 X 1.35 = 1.72X1014 kW

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