Answer:
[tex]F_{David} = 5N[/tex]
Explanation:
If the rope accelerates toward Stacy, then the force David applies is less than that of Stacy does.
By Newton’s Second Law the net force can be calculated.
[tex]F_{net} = ma = 5*2 = 10[/tex]
In that case, David pulls with 15 - 10 = 5N in order the rope to accelerate at 2 m/s^2.