Computing multiple stats

Let's now combine everything from the past two exercises to find multiple summary statistic with multiple groups in batrips.

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1
Group by start_station and end_station to calculate the mean duration and the total number of trips. Name these columns mean_duration and total_trips, respectively.
2
Group by start_station, end_station, and for each month in start_date to calculate the minimum and maximum duration. Name these columns min_duration and max_duration, respectively.