i want to send my question to expertS$$dzucker AG$,$ Meli$$ Hotels International S$.$A$.,$ Thai Airways Limited, and Tesco PLC$,$ respectively.

Required:

a$.$ Calculate gross profit margin $($gross profit$/$revenues$)$ and operating profit margin $($operating profit$/$revenues$)$ for each of these companies for the most recent year presented. If a particular ratio cannot be calculated, explain why not.

b$.$ Is it valid to compare the profit margins calculated in part $($a$)$ across these companies in assessing relative profitability? Why or why not?