PLEASE HELP IN PHYSICS!! (ENERGY)?

This questions have part A and B. I got part A right but i cannot seem to figure out part B.

The question is
NOTE EXPRESS ANSWER TO TWO SIGNIFICANT FIGURES.

The mass of a carbon atom is 2.0 x 10^-26 kg.
A) What is the kinetic energy of a carbon atom moving with a speed of 410 m/s?

i just used the kintetic energy equaiton KE=1/2mv^2 so KE=.5*(2.0 x 10^-26 kg)*(410^2)=1.7*10^-21 J

B) Two carbon atoms are joined by a spring-like carbon-carbon bond. The potential energy stored in the bond has the value you calculated in part A if the bond is stretched 0.050 nm. What is the bond’s spring constant?

so for this question i used F=-ky
F is already known from previous question and y is given in nanometers.
so i did
1.7*10^-21 / 5*10^-11 = 3.362*10^-11 == 3.4*10^-11 N/m

i tried this answer but got it wrong so i tried it with a negative sign and still got it wrong.
So i am not sure what i did wrong here or if my units are wrong? isnt the spring constant in N/m ??

Please help 🙁

Thank you

Comments on "PLEASE HELP IN PHYSICS!! (ENERGY)?"
More: A 2.500 g sample of uranium was heated in air. The resulting oxide weighed 2.949 gram. Determine the empirical formula of the oxide.? Please help me with these two Calc two word problems? Does anyone know what type of spider this is i think its a brown reclusive but not to sure anyway i can keep spiders out the house? Give the IUPAC name for each of the following compounds please.? A distribution is left-skewed?