Given that the lines are parallel, what would be the value of angle "a" in the diagram found below?

A right triangle is shown with angle B measuring 40 degrees. There is a vertical line A that is parallel to one of the sides of the right triangle that intersects the hypotenuse and is perpendicular to the other side of the triangle. There is an acute angle inside the triangle formed from intersecting this line and the hypotenuse.

a
40 degrees

b
90 degrees

c
60 degrees

d
120 degrees

e
cannot be determined

thanks!