# 9.5:  Write a function that takes one positional (required) argument and one keyword (optional)
# argument.

# Define function mul, which should take a required integer argument and an optional integer
# argument (keyword 'multiplier', with default 1.  If the optional arg is not passed, it should
# default to 1 (so that the argument value is multiplied by 1 and thus returned unchanged).

# your def here



a = 5

b = mul(a, multiplier=3)     # int, 15

c = mul(a)                   # int, 5

