A helium balloon on a string is tethered to a fence outside of a house. The altitude of the balloon can
be represented by the rational number 12 1/4 feet.
The string breaks and the balloon ascends 20 feet
per minute for 5 minutes. The helium then begins
to leak out of the balloon, causing it to descend at
3 1/2 feet per minute for 4 minutes. What is the
elevation of the balloon after it descends for 4
minutes?