4. (10 points) Some years ago T-Mobile (cell phone service provider) and Sprint (another cell phone service provider) merged (the current T-Mobile is the result of that merger). (a) Was this merger a horizontal merger or a vertical merger? Please give an explanation. (b) What impact did the merger have on concentration in the cell-phone service provider market (did concentration increase or decrease)? Please give an explanation. (c) Are there any circumstances in which a smaller number of larger firms in an industry can lead to more competition? Please explain