Multiply 37.75 x 4 to get the total number of hours Raphael worked the past 4 weeks. (The mean is just the total number divided by the number of parts).
37.75 x 4 = 151
Then, add 40 to that total to get the new total.
151 + 40 = 191
Now, divide that number by 5 (as in 5 weeks, the new number of parts).
191/5 = 38.2 hours