4) A train ticket in a certain city is $3.00. People who use the train also have the option of purchasing a frequent rider pass for $15.75 each month. With the pass, each ticket costs only
$2.25. Determine the number of times in a month the train must be used so that the total
monthly cost without the pass is the same as the total monthly cost with the pass.
A) 20 times
B) 23 times
C) 21 times
D) 22 times