Would You Ever Try This Out?

A $\text{40 kg}$ boy whose legs are $4 cm^2$ in area & $50 cm$ long, falls through a height of $2m$ without breaking his leg bones. If the bones of the legs can stand a stress of $9 \times 10^7 Nm^{-2}$ , calculate the magnitude of Young's modulus of the leg bone of the boy.

Details and Assumptions:

Give your answer in $Nm^{-2}$ .
Suppose your answer is $1.176 \times 10^{17}$ . Then write it as 1.176E+17