HELP: object.property returns undefined

let product = {
  name : 'Computer',
  inventory : 99,
  unit_price : 399.99

}
console.log(product);
// 2. Create a function named addInventory(). The function should accept 2 parameters -- the product object, and the number to add to the inventory. The function adjusts the product object's inventory property by adding the number passed into the function. 
// For example, if the inventory of the product is currently 2, calling addInventory(product, 3) will set the value of inventory to 5
/* Add a console.log() message to the function that includes a message that looks something like this:
"3 chairs added to the inventory"
In this example, "chair" is the name of the product.
*/
function addInventory(product, number) {
  product.name = product;
  product.inventory += number;
  console.log(number + " " + product['inventory'] + " added to invetory");
}

// 3. Call the addInventory() function
addInventory('computer', 1);
console.log(product.inventory); // returns 99 NOT 100