What is the total service revenue at March 31 and June 30, 2018?
{"": {"March 31, 2018": "", "June 30, 2018": "(in thousands, except share and per share amounts)", "September 30, 2018": "", "December 31, 2018": ""}, "Service revenue": {"March 31, 2018": 128706, "June 30, 2018": 129296, "September 30, 2018": 130139, "December 31, 2018": 132049}, "Network operations, including equity-based compensation expense": {"March 31, 2018": 54875, "June 30, 2018": 54379, "September 30, 2018": 54615, "December 31, 2018": 55660}, "Gains on equipment transactions": {"March 31, 2018": 117, "June 30, 2018": 357, "September 30, 2018": 416, "December 31, 2018": 92}, "Operating income": {"March 31, 2018": 20637, "June 30, 2018": 21354, "September 30, 2018": 22255, "December 31, 2018": 22311}, "Net income": {"March 31, 2018": 6784, "June 30, 2018": 6552, "September 30, 2018": 8231, "December 31, 2018": 7100}, "Net income per common sharebasic and diluted": {"March 31, 2018": 0.15, "June 30, 2018": 0.15, "September 30, 2018": 0.18, "December 31, 2018": 0.16}, "Weighted-average number of common sharesbasic": {"March 31, 2018": 44923973, "June 30, 2018": 45016767, "September 30, 2018": 45105830, "December 31, 2018": 45284481}, "Weighted-average number of common sharesdiluted": {"March 31, 2018": 45294697, "June 30, 2018": 45536473, "September 30, 2018": 45699635, "December 31, 2018": 45803418}}
total_revenue = df["Service revenue"]["March 31, 2018"] + df["Service revenue"]["June 30, 2018"]
answer = total_revenue