An Electron and a Positron, Both Essentially at Rest, Annihilate $9.11 \times 10 ^ { - 31 } \mathrm {~kg}$

An electron and a positron, both essentially at rest, annihilate each other, emitting two identical photons in the process. What is the wavelength of these photons? The mass of an electron or positron is $9.11 \times 10 ^ { - 31 } \mathrm {~kg}$ . $\left( h = 6.626 \times 10 ^ { - 34 } \mathrm {~J} \cdot \mathrm { s } , c = 3.00 \times 10 ^ { 8 } \mathrm {~m} / \mathrm { s } \right)$

A) $3.46 \mathrm { pm }$
B) $1.21 \times 10 ^ { - 12 } \mathrm { pm }$
C) $3.07 \mathrm { pm }$
D) $2.42 \mathrm { pm }$
E) $1.73 \mathrm { pm }$