A cell phone plan charges $39.95 a month plus 15 cents per text message sent and 15 cents per text message received. Using s to represent the number of text messages sent in one month and r to represent the number of text messages received in one month, the following equation can be used to calculate the total monthly cost, c: C = 39.95 + 0.15(s + r) If it is known that the total monthly cost is $53.45 and 63 text messages were received, solve for s, the total number of text messages sent.