I have two rails models, Usage & Price. So far they look like this:

```
class Usage < ActiveRecord::Base
    has_one :price

    def spend
        usage.amount * price.amount
    end
end

```

and

```
class Price < ActiveRecord::Base
    belongs_to :usage
end

```

I'm trying to call the "spend" by doing this in the console:

```
Usage.create(amount:100)
Price.create(amount:0.1)

usage=Usage.find(1)
puts usage.price

```

Where am I going wrong??