Code Snippet For Enabling Shipping Class

I have added this code snippet to enable shipping rates per line item in the cart:

add_filter( ‘woocommerce_package_rates’, ‘shipping_cost_based_on_number_of_items’, 10, 2 );
function shipping_cost_based_on_number_of_items( $rates, $package ) {
$numer_of_items = (int) sizeof($package[‘contents’]);

// Loop through shipping rates
foreach ( $rates as $rate_key => $rate ){
// Targetting “Flat rate” shipping method
if( ‘flat_rate’ === $rate->method_id ) {
$has_taxes = false;

// Set the new cost
$rates[$rate_key]->cost = $rate->cost * $numer_of_items;

// Taxes rate cost (if enabled)
foreach ($rates[$rate_key]->taxes as $key => $tax){
if( $tax > 0 ){
// New tax calculated cost
$taxes[$key] = $tax * $numer_of_items;
$has_taxes = true;
}
}
// Set new taxes cost
if( $has_taxes )
$rates[$rate_key]->taxes = $taxes;
}
}
return $rates;
}

However, along with this, I also want to enable free shipping for products with shipping class in cart. With this code in place I am unable to do that. What would be the code snippet to enable it and where should I add it in this code? I am using the latest version of Storefront theme.

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