Abriefcase falls from an ascending helicopter at 130 m. it hits the water 6.0 s later. what speed was the helicopter ascending at?

I'm guessing you're supposed to be using the 5 kinematic equation which use a, t, d, vi, and vf. because the helicopter and briefcase are moving together they have the same velocity so we can use the briefcase to determine the velocity of the helicopter. In the question we're given.
a= -9.81 m/s which is acceleration due to gravity
t= 6.0s
d= 130m
and vi, which is what we're looking for
so the equation we use is
d=vi (t)+(1/2a)(t)^2
130=vi (6.0)+1/2 (-9.8)(6.0)^2
130=6.0vi+-4.9 (36)
130=6.0vi-176.4
130+176.4=6.0vi
306.4=6.0vi
306.4/6.0=vi
51.066=vi
then round to significant digits and because the least amount is 2 when dividing 306.4 by 6.0 the answer is
The speed of the ascending helicopter was 51 m/s

Sub to pewdiepie he must stay #1