*Parts A and B, textbook solution:
Let AB be the originally horizontal ceiling, BC its originally vertical normal, AD the new ceiling and DE its normal. Then the angle BAD = . By definition DE is perpendicular to AD and BC is perpendicular to AB. Then the angle between DE extended and BC is because angles are equal when their sides are perpendicular, right side to right side and left side to left side.
Now CBE = is the angle of incidence of the vertical light beam. Its angle of reflection is also . The angle between the vertical incident beam and the reflected beam is 2.
Using the geometry of the triangle you set up the following relation:
tan(2) = y / x = 2.2 cm / 740 cm