How would I approach this problem using spreadsheet software? I typically use Excel.?

Say dealership A and B both sell a car for $20,600. Each will lower the cost of said car until the other is forced to stop selling the car. At the end of each day, dealership B’s policy will lower the cost of the car by 1% of dealership A end of day cost. Dealership A will lower their cost by $50. Of dealership B’s end of day cost.

I thought of using the forecast function but not sure how I would know the exact day which company would be forced to stop selling and what the final cost of each dealership would be.