oCustomersMail = customers.Any()
    ? customers.First(c => c.CustomerId == o.CustomerId).Mail
    : "Не найдено",

oCustomersMail = customers.Any()
    ? customers.First(c => c.CustomerId == o.CustomerId).Mail
    : "Не найдено",

    foreach (var activity in activities)
    {
        var latestStartTime = earliestStartTimes[activity.To] - activity.Duration;
        if (!latestStartTimes.ContainsKey(activity.From) || latestStartTimes[activity.From] > latestStartTime)
        {
            latestStartTimes[activity.From] = latestStartTime;
        }
    }

    foreach (var activity in activities)
    {
        var latestStartTime = earliestStartTimes[activity.To] - activity.Duration;
        if (!latestStartTimes.ContainsKey(activity.From) || latestStartTimes[activity.From] > latestStartTime)
        {
            latestStartTimes[activity.From] = latestStartTime;
        }
    }