Our company has started selling to larger customers, so we are creating subscription tiers with different feature sets to cater to our customers’ unique needs. We previously charged every customer a flat fee per month, but now we plan on charging for the number of users active on the customer's subscription plan. As a result, we're changing our billing system.
You’ve picked up the work item to implement the logic to compute the monthly charge:
Prorating Subscriptions (#8675309)
We'd like you to implement a monthlyCharge function to calculate the total monthly bill for a customer.