Young's modulus - 10 points first correct procedure?

Question

A force of 60 pN is required to stretch a sample of DNA of length 45 nm and Young's modulus 1.0x108 Nm2 by 15.0% of its original length. Determine the effective cross-sectional area of the DNA molecule in units of nm2.

Answer 1

F/A = E*deltaL/L0

A = L0*F/E*deltaL

A = 0.045*(60x10^-12)/((1x10^8)*0.00675)

A = 40 nm^2