The Slate Board of the Salted Hart

The inn called the Salted Hart chalks one line on its slate board for every barrel and crate in the cellar, and the potboy keeps rubbing them out crooked. The cellar-keeper wants the lines written the same way every time.

Write shelfLabel(name, count, price), where name is a string (the goods), count is a non-negative integer (how many are in the cellar), and price is a non-negative integer (the cost in coins of one of them).

It returns a string, built by these rules:

• If count is 0, return the name, then a colon, then a space, then out of stock — for example a name of Cider gives Cider: out of stock.
• Otherwise the total is count multiplied by price, and the line is the count, a space, a lowercase x, a space, the name, a space, =, a space, the total, a space, and then the coin word.
• The coin word is coin when the total is exactly 1, and coins for every other total.

No trailing spaces, no punctuation beyond what is described.