An electron from the n-side into the p-n junction through the depletion region and When it reaches the p-side it gains an energy equal to exponential barriers.

By conservation of energy,

KE before entering =ev +KE after reaching p side

$ \large\frac{1}{2}$$ \times m \times V_1^2 =e \times 0.5 +\large\frac{1}{2} \times$$ m V_2^2$

Solving we get,

$V_2 =2.7 \times 10^5 m/s$

Hence b is the correct answer.