The minimum cash balance of $20,000 is required in the Village of Sarahtown's general fund cash account. Transferring out of the account requires payment of $550 per transaction. Inspection of the variation of the account balance over the last year showed a variation of $9,000,000. The monthly interest rate is 0.0055. Calculate the following items:

1. The spread between the upper and lower limits

2. The upper limit

3. The return point

Explain your investment strategy to the village manager in a brief explanation.

Please provide proper calculations and explanations.