An author just signed a lucrative contract with a publisher that offers to pay her the amount of $$900$ at the end of year $6$ when the book is scheduled to be released. The author, being profligate, desires to receive a different package: an immediate payment of $$100$ that is followed by an annuity $($an equal amount$)$ to be paid at the end of each year for $6$ consecutive years. What annuity will make his package equivalent to the publisher's advance. Use an interest rate is $4\mathrm{.}00\%.$