Answer:
It's Option A.
Explanation:
Using the Cosine Rule:
cos < K = (3.9^2 - 1.9^2 - 2.8^2) / (-2 *1.9*2.8)
= 3.76 / -10.64
= - 0.3534.
m < K = 110.7 degrees.
Using the Sine Rule:
3.9 / sin 110.7 = 2.8 / sin <J
sin J = 2.8 sin 110.7/ 3.9 = 0.6716
m < J = 42.2 degrees
So m < L = 180 - (110.7 + 42.2)
= 180 - 152.9
= 27.1 degrees