Guess and Check #4

Each check I write costs 10 cents. I also have to pay a flat fee of 25 cents per month. My bank sent me a letter saying the fees were going to change. The new fee is 8 cents for each check and a flat fee of 50 cents/month. The bank said this would be cheaper for me because of the number of checks I write. What is the least number of checks I must write to make the new fees cheaper?

There are many approaches to this problem - one is to guess at what the answer might be, and then see how much it would have cost in the old system, and how much it costs in the new system. Try different guesses to discover where the "cross-over" point is. Be sure to explain the work you did to arrive at your answers!