The facts (in no particular order):

It costs you a $6,000 one-time fee to build your web site

You have three staff members, each costing you $60,000 per year

You spend $10,000 per year in marketing

The average pair of shoes cost you $10

The average price at which you sell a pair of shoes is $35

Each customer buys one pair of shoes each time they purchase

For each transaction you must pay a 4% credit card fee (e.g., to Mastercard, Visa, or Paypal)

Each customer purchases twice per year

The credit card fee is applied to the total amount that the customer charges, to include the shipping

For each shoe you sell, the amount of shipping is $8

Customers pay for shipping

Assume no other expenses or revenue (e.g., no taxes)

There are 28 days in a month

How many customers do you need to have in any given year to break even on that year?