Can someone please help me with this? easy question?

Consider a steel guitar string of initial length L=1m and cross-sectional area A=0.5mm^2. The Young's modulus of the steel is Y= 2.0 x10^11 pa. How far (delta L) would such a string stretch under a tension of 1500 ?

Express your answer in millimeters using two significant figures.

i need a step by step guide. the answer is 15mm but i keep getting 66.67mm.

what i did was,

1500/0.5mm^2 = 3000Nmm^-2.

then i convert 2 x10^11 Pa to Nmm^-2 = 200 000Nmm^-2

then, 3000Nmm^2 / 200 000Nmm^-2 = 0.015

using formula, (F/A) / (L/delta L) =Y,

1/0.015 = 66.67mm^2

that's what i got. i know it's wrong, so tell me where did i go wrong please..