Simulating a marketing campaign

Suppose you're working with a business and trying to estimate the potential performance of a marketing campaign. Before the business starts running their campaign with real money, they have asked you to build out a simulation where folks can tweak parameters and assess potential performance.
Given this context, write a marketing campaign simulation that fulfills the following requirements:

• Given a list of inputs such as conversion rate, cost, budget, etc -- return a list of newly signed up customers
• Define a function to simulate a cohort of customers -- given assumptions about spending and churn your function should be able to calculate the lifetime value of the cohort to the business
• Select some parameters, run thousands of simulations, and assess/summarize the results to the business

Note this is an example of a more open-ended/case study type question, so there is no exact correct answer. In an interview situation folks will be interested in your line of thinking and how well your code addresses the business problem.