Use the Koppelman dataset. Estimate conditional logit models similar to those reported in Table 26.1 but with the following modifications. For each case report the estimated coefficients and standard errors for the cost and time variables, the log-likelihood, and describe how the results change.

(a) Replicate the results of Table 26.1 for conditional logitwith the same variables. Note: the regressors used in Table 26.1 are cost, intime, income, and urban.

(b) Add the variable outtime, which is out-of-vehicle time.

(c) Replace intime with time=intime+outtime.

(d) Replace cost and intime with log(cost) and log(intime).