Math question please

Question

a cell phone carrier charges a fixed monthly fee plus a constant rate for each minutes used. in January the total cost for 350 minutes was $52 well in February the total cost for 300 minutes was $51. What is the constant charge for each minute use? what is the fixed monthly fee charged by the carrier?

Answer 1

52 = f +350m

51= f +300m

50m =1

m= 1/50= 2 cents per minute

f = $45 monthly fee