There are approximately 4 weeks per month.
Mr. Gleason will take home 1100 x 4 weeks = $4,400 per month.
The total budget - his take home pay is the amount his wife will need to make:
5,600 - 4,400 = $1,200
Now divide the total amount she needs to make by how much she brings home per hour:
1,200 / 10 = 120
She needs to work 120 hours per month.
The answer is D.