The ''Kangi'' is and earthen pot used to stay warm in Kashmir during the winter monts. Assume that the " Kangri" is shericla and of surface are `7 xx 10^(10-2) m^2` . It contains 300 g of mixture of coal. Wood and leaves with calorific value of 30 kj/g (and provides heat with 10 % efficiency.) The surface temperature of the "Kangri" is `60^@C` and the room temperature is `0^@C`. Then, a reasonable estime for the duration t( in hours) that the "kangri" heat will last is (take the "kangri" to be a black body).

Options

A. 8
B. 10
C. 12
D. 16