Douglas Whipple Corporation needs $$200$ million to expand its production and to develop new products. It has agreed to issue written pledges that it will repay a specified amount of money with interest on a particular day. Because it is uncertain it will have sufficient funds available if all of the pledges should become due on the same day, none of the pledges will be paid during the first $15$ years. After $15$ years, $10$ percent of the pledges will mature each year until all of them are retired at the end of the $25$th year. What are the pledges? Registered bonds Term$-$loan agreements Serial bonds Bond indentures