Angular Frequency ω= 140 rad/s =√(k/m) ,where k: Restoring Force; m: Mass
=> k= 140^2 * m
Force F(max)=k.Δx ,where Δx: elongation
=> k= F/Δx= 140^2 * m
Young's Modulus Y= (F/A)/(Δx/x)= (F/Δx)*(x/A)
,where A: Are of cross-section;x:Original Length
=>Y= k*(x/A) = (140^2 * m * x)/A = 4 X 10^9
Therefore, answer = 4