Sandy guarantees to pay Lester any debts Albert incurs with Lester. Sandy makes this guarantee because she knows that if she does not, Albert will run up a large debt with Lester and be forced to declare bankruptcy. Albert would then most likely be unable to pay Sandy what he owes her. Does this contract have to be in writing?

Answer: No

Explanation:

Main purpose rule, which is also known as leading object rule spares a contract to be written as person paying debt for any other person would be motivated because of gaining advantage by debt payment.

According to the question, contract is not required to be in written form as per main purpose rule. As Sandy is motivated to pay debt for Albert because she would be receiving benefit for herself. Albert will be able to pay Sandy if she pays debts of Albert to Lester otherwise Albert would become bankrupt.