1. Code the LISP macro, +=, which is passed a variable which it increments by the incrementValue and assigns the new value. The value returned by += should be the new value of numericVariable.

(+= numericVariable incrementValue)

Example:

> (setf x 1 y 10)

10

> (+= x 5)

6

> (+= y x)

16

> (print (list x y))

6 16