A person hired a firm to build a CB radio tower. The firm charges $100 for labor for first 10 feet. After that, the cost of labor for each succeeding 10 feet is $25 more than the preceding 10 feet. That is, the next 10 feet will cost $125; the next 10 feet will cost $150, etc. How much will it cost to build a 90-foot tower? Does this problem involve Arithmetic sequence or a Geometric sequence? And use the proper formulas where applicable???