Get the minimal fee for a transactions

dynamicFees.ts

const tx = {
  senderPublicKey: wallet.account.publicKey,
  networkIdentifier,
  nonce: wallet.account.nonce.toString(),
  passphrase: passphrase,
  asset: {
    fundraiser: fundraiser,
    amount: convertLSKToBeddows(amount.toString()),
    message
  }
};
const transaction = new FundTransaction(tx);
console.log(transaction.minFee.toString());