On a hot summerday, surface of the concrete highway may reach 328 K. Suppose a stream of wateris directed on the highwayso that the surface is suddenly lowered to 308 K. Time
taken in hours to cool the concrete to 318 K to a depth of 5 cm below the surface is:(Thermal diffusivity = 1.77 E-03 m$$^2$$/h)

A

1.2

B

1.4

C

1.8

D

1.6