4)
We woud apply the formula for calculating rate of change of momentum which is expressed as
F = m(v2 - v1)/t
where
F is the force
m is the mass of the object
v2 is the final velocity
v1 is the initial velocity
t is the time
From the information given,
m = 0.2
v1 = -13
v2 = 4
t = 0.5
F = 0.2(4 - -13)/0.5
F = 6.8 N