im on a test PLEASE HURRY! 21 POINTS On which triangle can the law of cosines be used to find the length of an unknown side? Law of cosines: a2 = b2 + c2 – 2bccos(A) Triangle Q R S is shown. The length of Q R is s, the length of R S is q, and the length of Q S is 12. Angle R Q S is 36 degrees, angle Q S R is 57 degrees, and angle S R Q is 87 degrees. Triangle Q R S is shown. The length of Q R is s, the length of R S is 7, and the length of Q S is 12. Angle R S Q is 57 degrees. Triangle Q R S is shown. The length of Q R is s, the length of R S is 7, and the length of Q S is b. Angle R S Q is 57 degrees and angle S Q R is 36 degrees. Triangle Q R S is shown. The length of Q R is s, the length of R S is q, and the length of Q S is 12. Angle R Q S is 36 degrees and angle Q S R is 57 degrees.