In \triangle P A T, \angle P=36^{\circ}, \angle A=56^{\circ}, and P A=10. Points U and G lie on sides \overline{T P} and \overline{T A}, respectively, so that P U=A G=1. Let M and N be the midpoints of segments \overline{P A} and \overline{U G}, respectively. What is the degree measure of the acute angle formed by lines M N and P A ?
Answer Choices
A. 76
B. 77
C. 78
D. 79
E. 80