A string of 4 mm in diameter has an original length of 2 m. The string is pulled by a force of 200 N. If the final length of the string is 2.02 m, what is the elastic modulus of the material?
a) 5.0×10¹⁰N/m²
b) 7.5×10¹⁰N/m²
c) 1.0×10¹¹N/m²
d) 1.5×10¹¹N/m²