<label>
    <input
        placeholder="Price"
        [ngModel]="price.snapshot"
        (ngModelChange)="price.setPrice($event)"
    />
</label>
<br />

<label>
    <input
        placeholder="Amount"
        [ngModel]="amount.snapshot"
        (ngModelChange)="amount.setAmount($event)"
    />
</label>

<p>Sum: {{ amount.sum }}</p>
