It is a very simple question to answer.
Obviously first we can calculate his weekly earnings and then multiply them by 4 to calculate his total earnings over the course of 4 year period.
So as he makes 6.2$ an hour. He will make 6.2 * 30 = 186 $ a week as that is the number of hours he works in a week.
Now we can multiply this by 4 to calculate his over all earnings. So 186 * 4 = 744.
