# 5.2:  Write a function greet() with one positional argument (a first name) and one keyword
# argument (an optional last name).  Make the default for last= the value None.  Call as shown.

# your code here


x = greet('Joe')
print(x)                 # Hi, Joe!

y = greet('Joe', last='Wilson')
print(y)                 # Hi, Joe Wilson!

