SOLUTION
We have been given the equation of the decay as

So we are looking for the time
Plugging the values into the equation, we have

Taking Ln of both sides, we have

Hence the answer is 4308 to the nearest year
She has extra because she only wants to make 80oz and it takes 8 and she has 30 so 30 is extra
Check the picture below.
let's recall that once we move an angle in the opposite direction of the 0-line or x-axis, we end up with a negative counterpart angle.
since we know that θ is on the IV Quadrant, then its negative counterpart must be across the line, and tangent is negative on the IV Quadrant, and positive on the I Quadrant.
The new image often has a ' next to it if this helps