Given ΔMNO, find the measure of ∠MNO.
Triangle MNO with segment LM forming a straight angle with segment MO and segment OP forming a straight angle with segment MO, the measure of angle NOP is 104 degrees, and segment MN and NO are marked congruent. 
28 degrees 
38 degrees 
52 degrees 
76 degrees 
I know the answer is 28 degrees , I just am not sure how to work out this problem .