Two parallel lines, ( e ) and ( f ), are crossed by two transversals. Horizontal and parallel lines ( e ) and ( f ) are cut by transversals ( c ) and ( d ). All angles are described clockwise, from upper left. At the intersection of lines ( e ) and ( c ), the angles are: 1, 2, 4, 3. At the intersection of lines ( f ) and ( c ), the angles are 5, 6, 8, 7. At the intersection of lines ( e ) and ( d ), the angles are: 9, 97 degrees, 12, 11. At the intersection of lines ( f ) and ( d ), the angles are 13, 14, 16, 15. What is the measure of ( ∠ 15 )?
a. ( m∠ 15 ) is equal to 77 degrees
b. ( m∠ 15 ) is equal to 83 degrees
c. ( m∠ 15 ) is equal to 93 degrees
d. ( m∠ 15 ) is equal to 97 degrees