9. Find x such that -x i + 2 j and 3 i + 12 j are perpendicular to each other. A. -8 B. 18 C. 8 D. -18 10. Use logarithms to evaluate (5.72)5. What is the answer? A. 14.8 B. 28.6 C. 3.20 D. 6.78 11. log4 X = 1; X = A. 4 B. 1 C.- D. 16 12. Simplify the following: 1403 A. 1 B. -1 C. i D.- i 13. Solve for the unknown part of the triangle, if it exists. If a = 50, b = 42, and C = 124, then what does c = ? A. 44 B. 88 C. 81 D. 28 14. Perform the indicated operation, leave the answers in the rectangular form a + bi. 1+ i 1 - 27 A. 3 +3/ B. -1+3/ 5 C. 1 - 3i D. -1 - 3i