Does spread() hold up for credits?

The assistant vouches for the billing helper that spreads a yearly amount across months, and gives a reason.

Your task

The assistant stands by the claim in claim.md. Reach a verdict and prove it with a run.

• verdict() judges what spread() does; the reason the assistant gives is for your write-up
• cases() returns the [total, months] pairs your run checks, totals in cents
• a verdict on its own does not count; the run has to show it
• leave everything below the dashed line alone; it is the code under test and the graded driver

The suite runs spread() on your cases at submit and checks the run settles the claim.