The General Spore
12 Monera Way
Plum, PU 43210
September 21, 1994

Calculus Student
Franklin & Marshall College
Lancaster, PA 17604-3003

Dear Calculus Student

It's hard to know how to begin this letter, after all you did. I have to thank you for rescuing me from that vile murder charge. Although I knew I was innocent, I was more than a little nervous that others might not agree - so I owe you a debt of gratitude.
I guess you don't really know much about me, other than the fact that I'm divorced from a pretty slimy cop ("Germy Jeremy", my friends call him). I'm a biochemical engineer, and I've been working on developing a heterotrophic bacteria which converts waste matter into energy. This is a fun field of work: converting trash into energy is a popular idea nowadays, since we seem to have too much of the former and limited supplies of the latter. Usually the conversion is done by burning, but I've been working on a cleaner, less toxic method. Since you cleared me in that last situation, I've been hired at a great company - it rather amazes me that they hired me, seeing as I was arrested on my way to the job interview. Nonetheless, they're an open-minded bunch of folk, and I really want to give them my all.
These bacteria that I've been working on die in exposure to sunlight, especially ultra-violet, which means that they're unlikely to be an environmental contaminant. But if you put them in the dark with a big, well-mixed tub of wet household trash, they reproduce (albeit fairly slowly), doubling their numbers every two months. (Some bacteria, such as E. coli, double their numbers every 20 or 30 minutes). And - this is the great part - every time they reproduce, they give off energy in the form of heat, which we can harness and convert into electricity. They generate energy in direct proportion to their growth rate; so the faster they reproduce, the more electricity we can make.
Right now I'm in the midst of working on a proposal for operating an experimental energy site on the banks of Plum Lake. Our biggest competitor is the King Coal Company, which certainly isn't known for its environmental concern. Even if I weren't applying for the position myself, I wouldn't want a coal company operating next to our lake. However, my personal interests make me doubly anxious to get this contract. The folks at The General Spore are very supportive and are encouraging me to give this proposal a lot of my time and (pardon the expression) energy.
The one thing I'm anxious about is making sure that I'll actually have sufficient bacteria to have the plant running at capacity within a year of start-up. I have exactly 125 pounds of bacteria now, in the freezer; by the end of twelve months, I'll need to have the bacteria multiplying at a rate of 2.7 tons/month or 180 lbs/day. The trouble is, I don't know how to figure out how fast they'll be multiplying by the one-year point. I know that in two months I'll have 250 pounds, and by six months I'll have one ton of bacteria, but I have no idea how to get a general formula for the number of bacteria on, say, the odd months-much less on days within the month.
Now, I know that this kind of stuff is probably really trivial to you, seeing as you're in Calculus, but it confounds me. Seeing as you've gone so far as to save my neck once already, do you think you could help me out with this? I just need a general formula for the amount of bacteria (by weight) on any given month; and I need a prediction as to whether they'll be reproducing fast enough on the last day of the year.
Thanks so much for your past and future help; I hope I'll hear from you one way or another by October 14.

Sincerely,

Grace Amazing

p.s. We are still searching for a suitable name for this bacteria. If you can think of a good name, please do suggest it to us!


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