Answer:74 ounces of milk
Explanation:
To calculate the total amount of milk William used, you need to convert the 4 pints of chocolate milk into ounces, as pints and ounces are different units of measurement.
1 pint = 16 ounces
So, 4 pints of chocolate milk is:
4 pints * 16 ounces/pint = 64 ounces
Now, add this to the 10 ounces of plain milk:
10 ounces (plain milk) + 64 ounces (chocolate milk) = 74 ounces
William used 74 ounces of milk in total when making the restaurant milkshake recipe.