Please help! photo is attached, will give brainliest.

Answer:84
Step-by-step explanation:
Okay. Are you taking calc? Dv/dt =d/dt(L(t)^3)=d/dt[(sqrt(14)+2t)^3]= 6(Sqrt(14)+2t)^2)=44. We defined t=0 to be time at which length is sqrt(14). Does that work?