At an effective annual interest rate $i,$ you are given:

i$.$ the present value of an annuity$-$immediate with annual payments of $1$ for $n$ years

is $40$ ; and

ii$.$ the present value of an annuity$-$immediate with annual payments of $1$ for $3n$ years

is $70.$

Calculate the accumulated value of an annuity$-$immediate with annual payments of $1$

for $2n$ years.

A $240$

B $243$

C $260$

D $268$

E $280$