A small copper ball of 5 mm diameter at 500 K is dropped into an oil bath whose temperature is 300 K. the thermal conductivity of copper is 400 W/m-K, its density 9000 kg/m$$^3$$ and its specific heat 385 J/kg-K, if the heat transfer coefficient is 250 W/m$$^2$$-K and lumped analysis is assumedto be valid, the rate of fall of the temperature of the ball at
the beginning of cooling will be, in K/s,

A

8.7

B

13.9

C

17.3

D

27.7