diatomic molecule

One description of the potential energy of a diatomic molecule is given by the Lennard-Jones potential,

$U\hspace{0.17em}=\hspace{0.17em}\frac{A}{r^{12}}-\frac{B}{r^6}$

where A and B are constants and r is the separation distance between the atoms. For the H₂ molecule, take $A\hspace{0.17em}=\hspace{0.17em}0.126 \times {10}^{-120} eV\times m^{12}$ and $B\hspace{0.17em}=\hspace{0.17em}1.489\times {10}^{-60} eV\times m^6$

(a) Find the separation distance r₀ at which the energy of the molecule is a minimum. (Give you answer to at least two decimal places.)  pm(b) Find the energy E required to break up the H₂ molecule. 
 74.1 eV

(b) Find the energy E required to break up the H₂ molecule. 
 2.79 eV

För A uppgiften räknar jag på detta sätt
$$\begin{gathered} r_0 = {\left(\frac{2A}{B}\right)}^{\frac{1}{6}} \\ {r}_0 ={(\hspace{0.17em}\frac{2\times 0.126\times {10}^{-120}}{1.489\times {10}^{-60}})}^{\frac{1}{6}}={(1.69241773\times {10}^{-61})}^{\frac{1}{6}} =\hspace{0.17em}7.4095\times {10}^{-11} =\hspace{0.17em}74.095 pm \end{gathered}$$

För B uppgiften räknar jag på detta sätt 

$$\begin{gathered} U\left(r_0\right) =\hspace{0.17em}\frac{A}{{r_0}^2}-\frac{B}{{r_0}^6} =\hspace{0.17em}\frac{0.126\times {10}^{-120}}{{(7.4095\times {10}^{-11})}^{12}}-\frac{1.489\times {10}^{-60}}{{(7.4095\times {10}^{-11})}^6} =\hspace{0.17em}-4.4758\times {10}^{-19} \\ \left|-4.4758\times {10}^{-19} J\right|\times \left(\frac{1 eV}{1.602\times {10}^{-19}}\right) =\hspace{0.17em}2.7938 eV \end{gathered}$$'

Bevisligen är ju detta fel men är det fel på räknandet, formeln eller nåt annat som ni kan se?