stuntman's vertical velocity is
vy= 6 sin 15=1.55m/s.
Height that he goes up is,
vertical kinetic energy = mgh
1/2 v² = gh, h=v²/(2g)=0.12 m.
time wanted to go up= vy/9.8=0.16s, Time to fall through a height
0.12+2.9=3.02m is
t=sqrt(3.02*2/9.8)=0.78 s
Total time needed to go up and down is 0.78+0.16=0.94 s.
to calculate the horizontal range,
Horizontal velocity = 6 cos 15=5.8 m/s.
Distance which he can cover is
5.8*0.94=5.44 m.
If the distance between the two building is less than 5.44 m then he will be safe and he can jump that distance.