The ancient Greeks labeled certain numbers as triangular numbers. The numbers 1, 3, 6, 10, 15, 21, and so on are triangular numbers. Complete parts a) through c) below. bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet bullet 1 3 6 10 15 21 Question content area bottom Part 1 a) Determine the next two triangular numbers. 1, 3, 6, 10, 15, 21, 2828, 3636 Part 2 b) Describe a procedure to determine the next five triangular numbers without drawing the figures. Choose the correct answer below. A. Square 6, 8, 10, 12, and 14. B. To obtain the 8th triangular number, add 8 to the 7th triangular number. To obtain the 9th triangular number, add 9 to the 8th triangular number, and so on. Your answer is correct.C. Double the previous triangular number and then subtract half of the previous from that. D. Add the last two triangular numbers together to get the next one. Part 3 c) Is 72 a triangular number? Explain how you determined your answer. Choose the correct answer below. A