For many materials, the constant C in the Larson-Miller parameter, P = (T + 460)(C + log10t) (where T is in degrees Fahrenheit and t in hours) is equal to 20. However, the Larson-Miller parameter can also be expressed as Pt = T(C t + ln t) with t in seconds and T in kelvin, using the natural logarithm of time. In these cases, what is the value of C t?