Answer:
d. not enforceable
Step-by-step explanation:
Usury state laws are strict in limiting the maximum limit among interest rates. If the usury statute limits the max interest rate to 3.5%, William's bank is violating it by putting it to 4.5%.
Usury laws are highly strict when it comes to regulations, so this kind of contract is not enforceable.
These laws are specifically tailored by the government to protect consumers from usury practiced by some banks and "loan sharks".