```
class CurrencyConverter {

    // 1
    private let conversionRate = 1.3 

    // 2
    private static let conversionRate = 1.3

    func convertToForeign(fromlocal local: Double) -> Double {
        return local * CurrencyConverter.conversionRate
    }
}

let c = CurrencyConverter()
print(c.convertToForeign(fromlocal: 5))

```

With reference to the code snippet above, assume that I need to use the constant `conversionRate` ONLY in an instance method.

What are the pros & cons of declaring `conversionRate` as only (1)`let` vs (2)`static let` ?

Which style would be more readable & optimised?

Additionally, let's say I will only need 1 short lived instance of `CurrencyConverter` and `conversionRate` itself is bulky (an array of 10K Doubles). Will (1)`let conversionRate` be more memory optimised?