A company is considering implementing a lockbox system. There is an annual fee of $5,660 plus a transaction fee of $0.05 per payment. The average size of customer payments is $2,790, and there are 24 payments made daily on average. The company can earn an EAR of 2.46% on its cash balances. For the lockbox system to be adopted with a positive NPV, by how many days should the average collection time be reduced at a minimum? Fractional answers are OK. (Assume 365 days in a year.)