title: ProviderError: transaction underpriced on Mumbai Testnet
body: <p>I am building an NFT Market on the Polygon network.</p>
  <p>I am able to deploy my code on localhost and everything works fine.</p>
  <p>But when I try to it deploy to the mumbai testnet using the command
  <strong>npx hardhat run scripts/deploy.js --network mumbai</strong></p>
  <p>I run into this error.
  <strong>ProviderError: transaction underpriced</strong></p>