Don is attempting to build muscle mass for his first body-building competition. according to sports nutrition experts, he should be eating grams per kilogram of bodyweight of protein per day.

1.2 to 1.7

Explanation:

Sports nutrition experts recommend a daily protein intake of 1.2 to 1.7 grams per body weight of a body builder.

For example, if Don weighs 80kg, the required optimal protein quantity in grams, that he needs to eat in building muscle mass for his first body building competition, should be between 96 grams and 136 grams. This is in accordance with the recommendations of the Academy of Nutrition and Dietetics.