A phone company offers two monthly charge plans. In Plan A, the customer pays a monthly fee of $20 and then an additional 6 cents per minute of use. In Plan B, the customer pays a monthly fee of $31.50 and then an additional 4 cents per minute of use. For what amounts of monthly phone use will Plan A cost less than Plan B? Use m for the number of minutes of phone use, and solve your inequality for m.