Fluid flows into a pipe at 300K. The surface temperature of the pipe is 450K, and the heated fluid leaves the pipe at 400K. The film temperature therefore varies from 375K at the beginning of the pipe to 425K at the end of the pipe. Say you want to use Equation 8.60 in Table 8.4 to calculate the Nusselt number. The temperature that you are going to use to determine the density and viscosity that you need for Re is K, and the value of the constant n in the equation is