A plane leave a certain airport from runway 4 RIGHT, whose bearing is N40degreesE. After flying for 1/2 mile, the pilot requestd permission to trun 90 degrees and head toward the southeast. The permission is granted. After the airplane goes 1 mile in this direction, what bearing should the control tower use to locate the plane?

After my work, I got S23.4degreesE but the book’s answer is
S76.6degreesE.

How do I get the book’s answer? Why is my answer wrong?