Given average of all prime numbers 60 and 80 is= 61, 67, 71, 73, 79

We know the formula,

 $\mathrm{Average} \left(\mathrm{A}\right)=\frac{\mathrm{Sum} \mathrm{of} \mathrm{given} \mathrm{values} \left(\mathrm{S}\right)}{\mathrm{Total} \mathrm{number} \mathrm{of} \mathrm{values} \left(\mathrm{N}\right)}$

 Here,

 Sum of given values(S)

=61+67+71+73+79

= 351

Total number of values(N)= 5

Substituting these values we get (A),

 $= \frac{351}{5}=70.2$

Hence, Option B is correct.