Как получить сумму всех тарифов

Я использую Laravel 5.7 и VueJs 2.5.* ...

Я хочу получить сумму всех тарифов на свой TotalFares. Я играл, но безуспешно ...

Вот мой Fares<Input>:

<tr v-for = "(ticketInvoiceItem, key) in form.ticketInvoiceItems" :key = "key">
  <td>
    <input v-model.number = "ticketInvoiceItem.fares" type = "number" size = "10" name = "fares" class = "table-control form-control" :class = "{ 'is-invalid': form.errors.has('fares') }">
    <has-error :form = "form" field = "fares"></has-error>
  </td>
</tr>

Вот мой TotalFares<input>:

<tfoot class = "tfoot">
  <tr>
    <td class = "table-amount">

      <input :value = "getFareTotal()" type = "text" name = "ticket_invoice_fares_total" class = "form-control" :class = "{ 'is-invalid': form.errors.has('ticket_invoice_fares_total') }">

    </td>
  </tr>
</tfoot>

Мой data() в VueJs:

data() {
  return {
    ticketInvoices: {},
    vendors: null,
    form: new Form({
      id: "",
      vendor_id: "",
      ticket_invoice_no: "",
      ticket_invoice_date: "",
      ticket_invoice_fares_total: "",

      ticketInvoiceItems: [{
        id: "",
        ticket_invoice_id: "",
        passenger_name: "",
        fares: 0,
      }]
    })
  }
},

Я пытался получить FaresTotal что-то вроде этого, но не смог:

getFareTotal() {
  let calFareTotal =
    parseInt(this.form.ticketInvoiceItems[key].fares) +
    parseInt(this.form.ticketInvoice.ticket_invoice_fares_total);

  this.form.ticketInvoice.ticket_invoice_fares_total = calFareTotal;

  return calFareTotal;
},