Jessica Young purchased a single$-$premium deferred annuity $($SPDA$)$ at age $30.$ The monthly annuity payments began when Ms$.$ Young reached age $50$ and continued annually for a period of $15$ years. With regard to this situation, it is correct to say that the accumulation period for Ms$.$ Young's SPDA was

$1$ month

$1$ year

$15$ years

$20$ years